it's possible to get to 5th, in fact even 2nd is possible, just extremely unlikely.
For example, if Lowry and Bargnani
play at an all star level, demar finally puts it together and JV can play like horford did in his 1st year, we could compete for the #2 spot, there is no team in the east that is all that strong. It's possible that 50-52 wins could get you a #2 seed this year, with a ton of teams in the 42-52 range.
I think being #2 - #5 in the east is just as likely at finishing in the bottom 3 in the league.