Of course the answer is 'yes', he can improve.  Many players improve between 27 and 32 and he should be able to.  I think the biggest improvment in player at this stage of their careers is above the shoulders rather than below.  
Guys who stay in the league can often take advantage of what they've learned and become more efficient/effective players.  I don't know Bass's intelligence but even a guy as impulsive (not dumb, impulsive) as Tony Allen seem to grow as players as they hit this stage if they can hang around long enough.  So, I expect Bass to be smarter on D and his positioning/spacing on offense and using his body on the boards.  I expect he'll become more confident in what he does well.  I doubt his shot will get better, or his handle, or his leaping ability, but being smarter by virtue of experience -- as long as he continues to work hard -- will allow for improvement.