If you're on T-Mobile USA and have been wondering where the heck BlackBerry 10.2.1 is, we now know thanks to comments from Mike Sievert, Executive VP and Chief Marketing Officer at T-Mobile. Taking to Twitter to answer questions for BlackBerry users, Sievert noted the delay is due to the WiFi calling integration on BlackBerry 10 devices which is a key offering from T-Mobile. 

So that's it. If you're not willing to explore the world of leaks and autoloaders, come early March we should see it rolling out to all T-Mobile customers. Great to finally have an answer explaining the delay, if only they had of mentioned that earlier instead of just ignoring the question altogether.