Yes! By buying it right now, you'll be guaranteed to get all 1.x.x updates, meaning that you won't have to worry about that for many years to come.
As a reminder, after 1.9.9 it's not necessarily 2.0, it follows itch's version control convention: major.minor.patch, so something like 1.999999999999999.999999999999999 is completely possible. 😅