Galaxy watch 4 rumors say that the OS will now become android instead of Tizen (similar to smart tvs) from its predecessor and some additional health monitoring items like blood sugar and blood pressure. Though watch 3 is on sale now (less 5k).
If those additional features are worth waiting for, then why not. Otherwise if watch 3 will give you what you need, I don't see why you'd wait for a more expensive one.
