No, that would just confuse Microsoft's mobile branding all the more. MS is in the phone business. They have a reasonably good OS with great hooks into their very mature suite of services, and once the agreement to use the Nokia name expires they'll sell the phones as Microsoft (or something--knowing MS they might just invent a new brand). Trying to maintain the BB brand in that mix would be a marketing nightmare.
They don't need another handset platform. I could see them buying BB's enterprise stuff, and it's not impossible that they might take the handset side in an attempt to migrate all those users to their own platform, but they wouldn't continue development on BB10 and they most definitely wouldn't grow the brand.
As I say, I think Google is at least marginally more likely to buy BB whole and actually maintain the brand for a few years.