Of course we will switch to it at some point or another, after honestly I am not in the race for the version (except for critical security updates).
My main priority is simple: the user experience. Will upgrading to Preact 10 change anything about the user experience? In my opinion, no.
So we will switch to it, but it’s not my top priority. My time is limited, and there are so many things to do, I prioritize 
After if you want to propose a PR for the migration, it will be with pleasure.