It doesn't really benefit Nintendo to buy them. If they wanted to buy a developer to leverage old IPs, they could just...hire more people. They don't need Capcom's bloated corpse to do that and it would be a lot less expensive to simply expand, nevermind the costs and time associated with changing their management to better fit a new corporate culture. The reason they haven't expanded that rapidly is because it's too expensive to do that and more expensive to just buy another company that's pretty large in size. So, if forced with that choice, they'd probably take the more conservative route there, which is the smart way.
Capcom's IPs don't have this untapped, limitless potential for everyone. Like, yeah, Resident Evil does pretty well, but Borderlands 2 did better, so you should probably roll your dice on making one of those rather than a series that is mostly critically mocked these days. No one is going to revive Mega Man. No one cares about Captain Commando.
On the plus side, outside of the situations I outlined before, it probably means no one's going to buy them that readily because it does have very few benefits. If it does happen (I'd bet on Tencent, if anyone), enthusiasts won't like the result.
