It's entirely possible that both suffer from sunk cost fallacy, and from that analysis there isn't a "better" or "more" sunk cost. It's already sunk, anything you sink further into it is a waste.
It will suffer the same same problems that Wayland has. the problem is that X is flawed at the design and level and whatever you propose that fix those design issues will face the same type of push-back from the communities that don't like it because it's not the way their grandpa taught them to do things.
keep in mind the wayland devs are the xorg devs that gave up on that project because how hopeless it was to fix things around.
Are we sure _this_ isn't the problem?