Jaylen will be offered an extension, but it certainly won't be for the max. My guess is somewhere around 4yrs/$90M and Jaylen will probably just wait.
It would probably be smart for the Cs to just match whatever contract another team offers for both players (unless Tatum just blows up this year - Jaylen's extension negotiations will take place this off-season). At the very least, if things aren't working out, they are only on the hook for 4 yrs and 5% raises rather than 5 yrs and 8% raises.
This is a terrible idea. It's one of the reasons why Hayward ended up leaving Utah, for example.
You're saving a pretty negligible difference to buy a lot of bad will from the player and agent.
If the players are in the territory of plausibly getting a max contract from another team, you offer them the max. If then there's a huge disconnection between the league-wide value of the player and how you value them, you trade him (or have done so already before the extension).
The Celtics haven't extended a draft pick since Rondo.
Don't expect Jaylen to sign one either, he and his agent are going to demand the max or close to it, I don't think the C's will pay that in October. I think they'll pay it after he shows improvement this year though.
I surely dont' expect Brown to be offered the max and wouldn't offer him one. I'd wait for the end of the season.
What I think is a bad idea is at the end of the year, the player being in max contract territory and the team playing those games of letting him sign somewhere and then match to save a few million.
I clarified my stance in my following post. I certainly stand by my point that you don't extend him for the max now, but we will have to see what happens this season. If another desperate team is offering Jaylen the max and he is coming off of a 14/5/2 season with decent efficiency, then I don't just automatically hand him the 5-yr max; I match and hope for the best. If he is putting up 20/7/5, then yeah, obviously.
Hayward was very close to staying in Utah and I don't think the decision not to give him a 5-yr max was a main factor. We had his college coach and were a better team. If it looks like Jaylen would bolt and he is a couple of years in on his contract, then we could trade him. It's not the end of the world.
Also, Jaylen doesn't have an agent since he doesn't think one person is qualified to handle all of his personal/professional interests. Instead he speaks for himself (exact words from Jaylen) and hires consultants if necessary.