Will the 521 get 8.1?
Yes. All WP8 devices will receive the 8.1 update.
And welcome to WPCentral. Cheers!
I have my doubts on "all" devices getting 8.1. But TMO has been public in saying the 521 and 925 will get this update.
No 8.1 as today! Too much promotion of 8.1 upgrade and so I am antsy for it! Come on T-Mobile! LOL!
8.1 Developer Preview works fine on my Lumia 521. It crashed only once, and I've been playing with It non-stop.
Does it have WiFi calling (I assume you are on T-Mobile, US)?