If I had to guess, Microsoft might be the one to acquire Spotify, especially since they're replacing the Groove Music with Spotify.
That would be pretty cool to me, and it might be a huge selling point for MS in general. Or MS would try too hard to Tailor it to whatever business model kick they happen to be on at the time and destroy it.
Don't expect Microsoft to buy anything like Spotify. They are backing away from the consumer market as quickly as they can without completely destroying their reputation. Dropping Groove Music is an example. They have abandoned their "Microsoft Band" sports activity watch line, without ever announcing it. They have all but abandoned Windows 10 Mobile, while denying it. The current CEO wants Microsoft to be a service provider to businesses, and nothing more. I'm not surprised that a company like Microsoft is allowing a CEO to rape and pillage the company to his own benefit when it has been done so often in other businesses and markets to their huge detriment, but I am disappointed.
In fact, I would not be surprised if consumer version of Windows 10 become so unusable in future that they lose their whole installed base in home PCs. All while showing better profits because they have cut costs from all operations to the bone, and initially they will be profitable serving business, until that bubble collapses. Remember IBM? Microsoft are too big to fail? Yeah, ever heard of Kodak? I worked for them, and saw from the inside how badly they had their heads in the sand over digital photography.
Anyway, a little OT, but the point is, streaming is a bad business model at the moment, because users want free music and won't pay enough to sustain it, and no one such as Microsoft is going to step in and magically make it work. I wish they would, but the middlemen who hold the rights to music also keep all the profits. Because that is what they have always done, and will do until the inevitable crisis in the music business hits.