It looks like Sprint is planning on launching their first WiMAX equipped phone by this summer. Speaking with Forbes, Sprint said that they're launching a WiMAX device in the first half of this year. Remember, WiMAX is 4G and Sprint's WiMAX network has been rolling out for some time now. A device to take advantage of Sprint's WiMAX network was bound to be released, this new timeframe is just a few months earlier than expected.
But what device could it be? Forbes cites the HTC Supersonic, which we've seen multiple times at Android Central in renders and product roadmaps and it would make a lot of sense. HTC has a good relationship with Sprint (it was the first carrier of the HTC Hero) and typically dabbles in top-of-the-line technology (Snapdragon, HD2) and plus, the name Supersonic could not be more fitting.
We'll likely find out more in the near future but in the mean time, just know that 4G is coming and an Android device being the first to use all that speed is a very real possibility.