Sprint has agreed to pay $5 billion on WiMAX so yeah, they're invested. LTE and WiMAX are what i've been reading up on for the last hour b/c my AT&T rep was asking (i work for radioshack) I think the technologies are so different you can't really compare them, each works differently and each has different advantages. and I think Sprint is betting on WiMAX because I wouldn't be surprised to see them try to turn full ISP for not just phones but computers and households in general
WiMAX:
http://en.wikipedia.org/wiki/Wimax
LTE:
http://en.wikipedia.org/wiki/3GPP_Lo..._LTE_Web_pages
and to answer the original question, I think everyone is gonna skip Rev B and go straight to 4G services