To answer triboy's original post, we are much further away than just Aldridge. He's a great player but Rondo+him is not enough. Smart could be an All Star one day (out of everyone on our roster), but he's 3 years away from that at best.
We'd need Aldridge and we'd need to add a solid defensive big like Asik. Good news is they are both free agents at the end of the year.
So Rondo, Aldridge, Asik, Green and Bradley- it's still not enough but you'd have to live with that team for at least a season while Smart, Sully and Olynyk get better.
You'd then hope that after a year, Smart can knock down the 3 pt shot at 35% and he can play Avery Bradley's role as the defensive pitbull- except he'll be on the rookie scale deal.
Green will be gone so you'd need to find another wing that can shoot the three and defend, with Bradley coming off the bench.
I'm saying that this team's current roster with Aldridge added would still need Smart to become a top 20 NBA player to be a true contender- before Rondo turns 31 ideally. That's 3 and a half years from now. Pretty unlikely but possible.
You need that third star player who is at least an All Star caliber player, and a big man to patrol the paint so Aldridge can drag his defender out to 15 feet and work his magic.