Xperia Z4

Curiously, Sony didn't show off a new flagship smartphone at Mobile World Congress last month, instead opting to refresh its tablet lineup and show us some new mid-range phones. We're still expecting an Xperia Z4 before long though, and given the company's solid track record with the Z3 and Z3 Compact, Sony's next big thing promises to be one of the more interesting high-end Android phones of the year.

So what are our hopes for the new Sony flagship? We've got a list prepped after the break.

READ: The Sony Xperia Z4 wishlist

New camera hardware

Sony camera

The sensor used in the last wave of high-end Xperia phones, a 20.7-megapixel Exmor RS unit, has featured in three generations of phones to date. Though the optics have changed somewhat, the most important piece of the camera hardware equation has remained unchanged since the Xperia Z1. And while it's held up relatively well, it's definitely starting to show its age. In the Xperia Z4, Sony needs refreshed camera hardware if it's going to compete against the Galaxy S6 and iPhone 6.

After more than two years, Sony's 20-megapixel sensor is starting to show its age.

Compared to the high-end phones of 2015, Sony's 20-megapixel sensor has a tendency to capture somewhat mushy, washed-out images in fading light, with plenty of noise in night-time scenes. Sony's doing a lot of good stuff with oversampling, taking a 20-megapixel sensor and producing generally solid 8-megapixel shots. But it feels like a crucial piece of the puzzle is missing — in 2015, if you're going with a high megapixel count (and thus smaller pixels on the sensor), you need optical image stabilization to back that up. With OIS thrown into the mix, Sony would be free to take longer exposures, thus reducing the graininess and noise associated with its current sensor.

As it stands, the rumor mill suggests Sony may introduce a new image curved sensor into the mix in its next flagship phone. That technology is certainly in the works, though we'll have to see whether it's ready in time for the next major Xperia launch.

Wireless charging

Qi coil

For a while Sony has included proprietary magnetic charging ports in many of its high-end Xperia phones, and even some tablets. These are a convenient way to charge your phone without dealing with wires, or the annoying plastic flaps covering the phones' microUSB ports. The problem is they're proprietary, and Sony charges a sizeable sum for what's essentially a magnet attached to a piece of plastic with a USB cable inside. It's also non-standardized — upgrade from an Xperia Z1 to Z3, for instance, and you'll find the charging dock doesn't quite fit.

Qi charging would be a great replacement for Sony's proprietary magnetic docks

Wireless charging, hopefully using the widespread Qi charging standard, would give the Xperia Z4 a more convenient charging method. It'd also go hand-in-hand with Sony's strategy of introducing "two day battery life" across its entire range of phones. With periodic charging over Qi, it'd be much easier to keep your Z4 alive for multiple days without running into any range anxiety.

Sony has been looking into faster wireless charging technologies in the past couple of years, with research focusing on getting a smartphone charged from dead to full in just one hour. We'd be happy with just a standard Qi coil at this point, though.

MORE: Wireless charging, in plain English

No more plastic flaps

Charging flaps

... Or at least few plastic flaps where it matters. Samsung, HTC and others have figured out how to do water resistance without annoying, fiddly plastic covers. We hope Sony can do the same in the Xperia Z4, while keeping the waterproof credentials that have become a point of differentiation for its Xperia lineup.

Doing water resistance without annoying plastic covers isn't difficult.

Sony has already done away with plastic flaps on the Xperia M4, without compromising that phone's underwater capabilities, and early Z4 leaks suggest the next Sony flagship could be headed in this direction too.

We're fine with keeping SIM cards and microSDs behind plastic doors — after all, you're not fiddling about with these on a daily basis. But if Sony can eliminate one of the regular annoyances involved in charging its phones over a USB cable, it'll be onto a winner.

For it not to be replaced six months later

Sony Xperia Z series

With Sony's typically rapid release cycles, where a new flagship usually emerges every six months, Xperia buyers at the high end have found themselves in something of a predicament. Even if you buy a new Sony phone right as it's released, less than half a year later your phone is no longer the new hotness. It's a legitimate point against purchasing a Sony phone when there's a reasonable guarantee that other manufacturers' are pretty much guaranteed a year as the top dog.

Sony's rapid refresh cycle isn't just a source of anxiety for consumers — it's also a business problem.

And though Xperia Z2 updates haven't lagged too far behind the Z3 series, it's clear which is going to be the greater priority for Sony's engineers when it's time to roll out a new version of Android.

It's also a business problem for Sony. Unless you're Samsung or Apple, U.S. carriers like you to release one major high-end phone per year, not two, and the rapid rate at which Sony burns through flagships surely isn't helping its flailing U.S. mobile business. And it's also worth pointing out the added research, development and engineering costs of fielding a new flagship phone every six months.

With Sony likely moving closer to the middle of the year for the Xperia Z4's launch, it's less likely that we'll see a Z5 later in the year. Sony's end-of-year refresh typically comes at the IFA trade show in Berlin each September, and a summer launch would likely preclude that. So we hope this is a sign of Sony switching to a traditional annual refresh cycle for its high-end phones.

MORE: In Pictures: Three generations of Sony Xperia flagships

A Compact version

Xperia Z3 + Compact

The Sony Xperia Z3 Compact — and the Z1 Compact that preceded it — were two of the most interesting Android handsets of 2014, for the simple reason that Sony is just about the only manufacturer that's serious about bringing a high-end Android smartphone experience to a sub-five-inch form factor.

Sony is the only Android manufacturer taking small phones seriously.

Simply put, if you want a good high-end Android phone that's not huge, Sony is the only game in town. Combined with the aggressive launch price (in Europe, at least) for the Z3 Compact in particular it's a real differentiator for Sony. Most other manufacturers' "mini" Android phones feature disappointing specs and compromised user experience in addition to their smaller size.

For that reason we'd love to see Sony continue this trend, and release an Xperia Z4 Compact at some point this year. There's no denying the popularity of big Android phones, but there's an equally important audience that wants a high-end Android experience in a device around the size of an iPhone 6, and Sony is best placed to cater to them.

MORE: Sony Xperia Z3 + Z3 Compact review

What do you want to see from the next Sony Xperia flagship? Share your thoughts down in the comments, and stay tuned to *Android Central for more Z4 coverage as the launch approaches!*