Most responses I see to this question are the same camp: setting new default apps won't be available until the fall since developers needs to submit updates to their apps that include iOS 14 APIs and apps with code for iOS 14 won't be approved until official release.
Ahh, okay. Still, it's something to look forward to.
I really look forward, also, to 3rd party homepage widgets. It's going to be interesting to see what developers are going to create.