There have been some interesting observations on HN and elsewhere, that Canonical for a long time didn't know what it is doing, starting and cancelling projects, but in last years it is lowering interest in desktop and is more focused on providing cloud server software and foisting its new products and methodologies on its users(snap). Some people see this as indication that Canonical is positioning itself to be bought for the best price. It makes sense, as Canonical has a large Linux user base but can't make money there. Microsoft is making inroads in Linux world is the most likely buyer.

there has been some collaboration between the two, however MS collaborates with other small companies and that speculation never arises. I wouldn't set a bet that they're uninterested in Canonical, but the desire to buy it has always been overstretched, it is much bigger chance that they buy some other specialized distro vendor instead (like Google buying Neverware). Ubuntu is too generic in that sense.

But it is still a task, isn't it? So, now you move to Ubuntu, then if things get south, you move to Debian. Or, you could move to Debian or other less risky distribution now and likely save some time and energy.

On the other hand, maybe Ubuntu is providing something special that Debian can't do - then it may make sense to go with Ubuntu and maybe even swallow Microsoft's fishing hook if it comes.