If you've given up refreshing the Play Store listing for the Nexus 4, we wouldn't blame you at this point. There's no indication when these will be back in stock from Google directly, and that's really unfortunate. If you do happen to go to the Play Store though, you'll be greeted with a "Special Offer from T-Mobile" notice. If you follow the link, you're taken to T-Mobile's online store to buy it on-contract for $199. Curiously enough, this is showing up on both the 8 and 16GB models -- odd considering that 16GB is the only capacity sold by T-Mobile.
This really doesn't make any sense to us. Google has put the Nexus 4 at an extremely aggressive price point, one that's meant to show the great value of buying it directly from the Play Store. Pushing users to the more expensive on-contract option just because its out of stock at the moment is very odd. Google pushing the device with a contract from T-Mobile seems to go directly against what it's trying to accomplish with the "Devices" section of the Play Store.
Source: Google Play Store