I'm going off Metro's official announcement.
the transaction is complete, MetroPCS and T-Mobile will be, and continue to operate as, independent companies."
"According to the Wall Street Journal, both networks will keep running until the end of 2015, when the MetroPCS network will be shut down. That means MetroPCS consumers won’t have to rush out and get a new phone any time soon. And when customers do have to buy a new phone, they will be automatically moved over to T-Mobile’s network."
But honestly it doesn't matter. Got a long time till anything happens so A LOT could and will prolly change.