While Microsoft is a rival of Apple and Sony, I doubt they're going to entirely remove the availability on those platforms. At most, maybe increase the price a bit or reduce focus and updates.
Let's take an example: Microsoft Word, Powerpoint, Excel, etc. - the whole MS Business category.
They're available on Macs, but don't you have to buy them?
Mojang (possibly turning into Microjang LOL) makes a large amount of money off of the sales on Sony and Apple platforms.
And also, people who already bought the game on Sony platforms.. if they had the game removed or never updated again, Microsoft would lose a LOT of reputation and credibility, plus it'd receive a flood of complaints.
However, I still do hope that Mojang doesn't go through with this deal.
While they might gain extra developers and available resources, they would lose their individuality and room for creativity.
Ever heard of "Common Core" within the USA?
It's basically a big system for schooling. Every class has to go ___this way, and you have to teach it in ____this manner. It really restricts the teachers' freedom, and teachers hate it.