I don't know about that. I'd be very surprised if anyone pays Ariza or Morris $20 million per year. That amount seems high for Barnes and Rubio also, although somewhat more likely.
As for the rest of the list, some of them will be pursued in the early going, but a lot of them will be lucky to get anything over a few million per year.
It's true that there are going to be a lot of free agents, but there won't be that many that people want. That's what's going to drive up the price for the top couple of tiers. Also, some of them are virtually certain to re-up with their current teams (Irving, Porzingis, Towns), so they aren't really on the market.
I think a safe guess is that Oubre will get $80M/4y from someone.