Not impossible, but I'm not sure how likely that is.
I understand why Motorola was sold and what Google and Android gained from it. Beyond shedding an underperforming business unit, I wouldn't understand what MS or WP stand to gain from selling Ex-Nokia to someone else. That move would be almost exclusively about cutting financial losses. Not that savings aren't important, but in contrast to the Motorola deal, selling Ex-Nokia achieves no strategic advantages for WP or the Windows ecosystem. It's actually more likely to introduce a rather large threat to the WP ecosystem, as it might leave it without any OEM backing whatsoever.
It wasn't too long ago that the entire business world discussed how Nokia somewhat "forced" MS into buying Nokia. Even WCentral reported on how events unfolded from that perspective. I have trouble imagining that the entire landscape has since shifted, in the sense that MS now sees absolutely no value in holding on to a company, which they just recently felt was a company they couldn't afford not to purchase.
I really have no idea, but based on what I currently know, I'm thinking another round of massive layoffs are more likely, combined with press statements discussing how MS intends to "streamline" the WP product portfolio and therefore requires fewer people to develop and support a smaller set of SKUs. No idea if that's correct. Just my best guess right now.