that's an issue microsoft has to deal with, not the devs.
Viewing post in Super Smash Bros. Crusade comments
oh no, the game's definitely gonna get updates.
it's just that it'll not work on latest windows versions if microsoft doesn't do anything. you gotta remember, the game runs on gm8, there's genuinely not much to be done.
especially since porting to like, gms2 or something would take a LOT of time and manpower that there's just not enough of.