Perhaps more adventurous, integrating Skype-like functionality into Windows Phone would be something of a game-changer.Integrated multinational Vo IP support would potentially be enormously disruptive to the cellphone market.
The technology isn't good enough and the users aren't lucrative enough or plentiful enough to justify it.
Similarly, although Skype is in many ways a better instant messaging and voice- or video-calling client than Live Messenger, it's hard to believe that it's billion better.
The Skype client itself is written almost as if it were a piece of malware, using complex obfuscation and anti-reverse engineering techniques, and it would be disquieting for Microsoft to release something that behaved in such a shady way; at the very least, the client would surely have to be rewritten to avoid the obfuscation and outright hostility to managed networks that Skype currently has.
Especially as there's likely to be quite a bit of overlap between the customer bases: People aren't giving Skype the money instead of Microsoft because they prefer paying Skype, they're doing it because Microsoft simply doesn't sell Skype-like telephony facilities.
And Lync customers are already on the payment treadmill, so it should be far easier to extract further payments from them for additional services.