If Nurkic is interested in a deal substantially less than the max right now (to lock in generational wealth a year early), then signing him this off-season makes sense. If he either wants the max or something close to the max, then wait for next off-season and match. An extra year of information is important. It's not just health--remember that Nurkic went from "center of the future" to out of Denver's plans. He certainly played amazingly well for Portland, but it was for 20 games. Players have had unsustainably hot quarter-season stretches before. Not that I'm forecasting that for Nurkic, but if you see him play at that level for a full season, there's far less uncertainty in valuing him as a max player.
It's far more important to get this right than to save a few million dollars per year, IMO. If the worst should happen and Nurkic suffers a major injury or regresses back to decent-but-not-great, you're not staring at yet another albatross of a contract.
Again, I'm not saying that that's the likeliest scenario, but Portland gets another year to wait and they should take it.