I see a few different scenarios for the C's here:
1) Pay him a max (most likely) or near max contract, which will take him through his early to mid 30's at 25-30 million a year.
2) Take the Harden route and extend him before he is a free agent.
3) Trade him before his max contract and go with someone else.
The way I look at it Isaiah is a Celtic for the time being so there is not much for us to worry about. I will be interested in seeing how he plays this year and how the Nets pick starts looking over the course of the season. There are a couple of good PG's in the draft next year, plus Rozier is looking like a guy who is making some quality progress.
I am very torn on Isaiah because he was by far our best player last year (IMO) and yet I do not want to give him a max contract when this one runs out. For all the praise we give IT (and he deserves a lot) he is a guy who shot 42% from the field two years ago (combined between PHX and BOS) and 43% last year. Those numbers drop below 40% for the playoffs. Not exactly high efficiency when it comes to shooting. He does seem to have a tendency to play hero ball from time to time, but given the lack of scoring options the C's had last year it is hard to blame him. I don't think he is best suited as a number 1 option on a team, but I think he has earned the role of a starter. Is that a max contract player?
I have had a very hard time coming around on the idea of IT as a max player, but at the same time I have loved his passion for the organization and history. He has become a vocal part of our team on and off the court.
It will be interesting to see what choice the C's make with IT.