It's unlikely - if the Ubuntu activities at Dell turn a profit, Microsoft will have to make a convincing case that not being Windows-exclusive is somehow detrimental to longterm strategy, and that's going to be a tough sell. Dell is one of (the only?) major player with an offering to a new (and very influential) market.

Nokia is different - Microsoft wasn't displacing a successful smartphone business, they bailed out a massive clusterfk. Maemo was promising, sure, but in no way profitable. Basically, Nokia wasn't in a place financially to make a long bet on a new player in the smartphone OS market - Microsoft was.