According to
CNews article, this would be very probable scenario:
"I believe XMPP is the right platform through which to deliver interoperability with at least some of our partners," Dietzen said in an interview.", said Scott Dietzen, Yahoo's new head of communications products including Yahoo Messenger and Yahoo Mail.
Scott, and what about SIP/SIMPLE?
"There are two competing potential standards, XMPP and...SIP. If I were betting, I'd bet on XMPP emerging as the likely framework for adoption."Seems that Yahoo! heads made their choice, and that's great news for XMPP community!