How many roster changes are too many to keep/maintain the "culture" that Stevens has built in Boston?

I have no question that our 15 man roster from this season will not all return for next year, but how many guys can we lose from our current roster (other than James Young) and still maintain the culture that Stevens and his staff has done so well to build in his first three years?

Ainge has salary cap money, young players on fairly cheap contracts to possibly trade and eight 2016 draft picks as well as bunches of other picks in the next two drafts as well.  He is also committed to improving our roster, so moves will be made and some of "our guys" could be moving on.

I really liked our team this year.  They were not talented enough to beat the Hawks, but played hard in almost every single game all year.  They often
fell behind early, but battled back in almost everyone of these types of games to almost always make each game a winnable game even if they did end
up losing it.  All of their team stats were better when compared to last season, and just about every player has improved.

Clearly, what Stevens has accomplished within each of his first three seasons has been very impressive as far as developing the culture that has allowed
us to go from 25 wins to now 48 wins in only the last two off seasons.  He not only makes every player better, but he is apparently very understanding
of building a team that plays hard, does not whine in the press and has guys that all genuinely like each other, etc, etc.

I am very hopeful that with so much money to spend and such a strong desire to get much closer to banner #18 that the team atmosphere does not
radically change.

Your thoughts??

my guess is we will 4-5 new players next year.

a couple rookies and either trades or FA for the others.