Assuming he stays relatively healthy for the next 5 years, here's a rough guess about where he'll rank among all guards during the times they played with the franchise:
Regular season, per game
12th in points, 4th in rebounds, 1st in assists and steals
Regular season career totals
5th in points, 3rd in rebounds, 1st or 2nd in assists, 1st in steals
Playoffs, per game
7th in points, 1st in rebounds, assists and steals
Playoffs, career totals
3rd in points, 1st in rebounds, assists and steals.
Note: steals weren't counted for Cousy/Sharmin/Sam or Casey Jones
That's fairly conservative, based on numbers slightly worse than he's put up recently but slightly better regular season scoring, 350 out of the 410 available regular season games, 35 playoff games compared to the 92 he's played in the last 5 years. He'd be 31 at the time, so he could easily go a few years beyond that.