That's a LONG wait...
I figure if they are not going to start until 2013, don't expect them to finish roll outs until 2015.
Verizon should finish it's rollouts this year or by this time next year, and AT&T a year later from that since they started late.
Anyone getting an HTC OneX(L) now simply because it "could" be compatible with T-Mobile's LTE network a year later could be in for a shocker announcement that it's not compatible with the network, not to mention the phone could "almost" be obsolete by then.