At the 4G world yesterday, AT&T outlined their LTE, and consequently their voice over LTE, plans.
This is my favorite slide, the one that says "VoLTE in 2013", with the GIANT CAVEAT "Expected pending standards".
Does that mean they have actually committed to a technology which still isn't defined? Of course there are many, many IMS/SIP/VoIP specs floating around, but if I were a vendor for this solution, I'd be a little nervous.
Notice that Verizon, in their announcements at CTIA, simply declined to talk about voice over LTE. CS Fallback is still a lot of work, and VoLTE/IMS is still a long ways out.
I wonder if Verizon's VoLTE will work with AT&T's VoLTE...