A few things.
1) There is almost no chance that Sully will end up signing for anything less than $10M a year based on talent / youth alone. He is a 23 year old guy with career 16/10/3 Per-36 numbers in a league where Iman Shumpert (a 25 year old with career 11/5/3 Per-36) got $9M a year.
2) The dramatic (around +$20M) rise in the cap means that there are going to be probably about 20+ teams who have enough cap space to sign at least one max contract player. This means it's going to be a buyer's market in a huge way - teams will be trying to outbid each other for the top 10-15 guys on the market, and it's going to drive contracts up in a huge way as a result.
3) The 2016 free agent class is basically structured like this:
Top Tier (stars):
Kevin Durant
Dwyane Wade (likely to remain with Miami)
Kobe Bryant (likely to retire)
Andre Drummond
Al Horford
Bradley Beal
Second tier (borderline stars):
Rajon Rondo
Mike Conley
Al Jefferson
Brandon Jennings
Eric Gordon
Joakhim Noah (despite his low mins, teams WILL chase him)
Third Tier (prospects with star potential):
Evan Fournier
Harrison Barnes
Tony Wroten
Jared Sullinger
So that's basically anywhere from 12 to 15 players who are above Sully in the Free agent market, but only about 4 of those (Drummond, Horford, Jefferson, Noah) are bigs. That means that once those top 4 bigs are signed to contracts, every remaining team who needs a skilled big man will be getting in to a bidding war over Sully - all armed with enough cap space to give a max contract.
It's a dream scenario for Sully. As long as Boston continues to limit his minutes to no more than about 24 or 25 a game he should continue to perform as beastly as he has thus far - and as long as that's the case, it's almost certain that there will be at least 3 or 4 teams fighting hard for his services.
Look back in history and you will see how things worked out for guys like Omer Asik, Josh Smith, Tristan Thompson, Chandler Parsons, etc. All it takes is for one team (out of 30) to be willing to stupidly overpay, and before you know it you have Sully signed up on a max deal.
The thing is, Danny and Stevens no doubt know that Sully's performance this year won't be sustainable if he is ever asked to play anywhere near 30 minute a game. His percentages will all drop to the floor.
So the best thing they can do is play him < 25 MPG (and hide behind Bostons front-court logjam as an excuse) so that he continues to produce great all season and pump up his trade value - then pull a trade before the deadline.
It's the best scenario for Boston, really. As much as I would like to see Sully here, I am extremely confident that some team is going to overpay for him next season. If that happens Danny has two options:
1) Match the offer, and end up committing way too much Salary to a guy who can't play more than 6th man minutes
2) Decline to match, and watch him walk away for nothing
Neither is a great scenario to be in, so orchestrating a trade (and getting something back) seems like the best way to go.
Yeah I know - it's sad to see him go. I know, he's playing great. I know, we'd like to see him back. But Danny has always handled his role with a "business first" mentality, where he makes deals with his head over his heart. Your heart would tell you to match and keep him here, but your head will tell you that's not an option.
Interesting analysis. I'd look at it this way though, you aren't paying max money for a backup. So what teams could Sully realistically start for right now, either at an undersized 5 or as a four. There aren't as many starting gigs as you'd think.
Off the top of my head?
Chicago (upgrade over Gibson and Mirotic, and Noah is likely gone in FA)
Brooklyn (They'd be better off with Lopez/Sully/Young than Lopez/Young/Johnson)
Charlotte (Jefferson is a FA, and Sully is better than any of their other bigs)
New York (Probably an upgrade over Robin Lopez)
Indiana (better then Mahinmi, Hill and Allen + would allow George to move back to SF)
Toronto (he's better than any big on the roster other than Jonas)
Washington (significant upgrade over Hump)
Denver (possible upgrade over Nurkic, and a good match with Faried)
Golden State (Bogut only has so much juice left in him, and Sully+Green would work well)
Dallas (definite upgrade over Pachulia / McGee, and they somebody to carry on form Dirk)
Timberwolves (he might fit better with Towns than Dieng does)
Houston (slight upgrade over Jones, who may leave in FA)
Portland (upgrade over pretty much every big on their roster)
Phoenix (upgrade over Morris, who has also been disgruntled since his brother got traded)
OKC (upgrade over Asik, Perkins and Anderson)
San Antonio (potential replacement for Duncan, likely to retire soon, in a Sully/LMA frontcourt)
Not all of these are likely, but they're all possibilities.