MS clarifies: monetization of Live does not involve the MSP
"Potentially Yes, I think that the model that we have right now with the Xbox Live is is the one with which we will continue to work. And a real success for everyone.  Users are  very satisfied  and is easily understandable , and this is the most important thing. So don't make changes for now. "
Therefore there remains still open the question of the "monetization", although in February, Michael Wolf, XBLA global marketing manager, had stated that MS was considering the introduction of "freemium" games, or titles that you can download and play for free but requiring payment of small amounts to obtain competitive objects or more levels. And even that might be a way to "monetize".
Then it only remains to wait for more official news.