Depends. If it's 5e with its flaws fixed, or a new edition which solves the issues I have with the system. Then yeah sure I'll buy it. Doesn't matter if it's backwards compatible or not if they do it right imo.
If it's just 5e, but not backwards compatible smoothly, but also doesn't actually fix any problems I have with the system. And then goes and doubles down on every single thing I dislike about it such as oversimplification and removal of significant player choices, then I'm definitely not buying it.
Judging from the current design direction, I'm 90% sure it will be the latter.