As I see it, we only have six NBA calibur players, that is players solid enough to play for a championship team. And several of them are undeveloped at this time, like Speights, Young and Williams.
We had a .500 ball club this season, maybe a few games better, but injuries and bad coaching got us .500. if you add Brand to that group you get a playoff team, maybe a 50-55 game team, but not quite at the level of a Boston or Cleveland as they are this season.
Dalembert, Evans, Green, Ivey, and Rush are all pretty sub-par players. Sam has been a real disappointment, he's too much of a head-case to be reliable. Jason Smith is probably a borderline player at best.
Assuming we keep Miller, we'll have him, Brand, Iguodala, Young, Williams and Speights. That's an ok group, but unless the four young players in that group improve dramatically, it's not even a core for a championship team. We need a better center and a better point guard, just for starters, and then we'll need backups at all the positions as well.
Replacing Sam will probably be the hardest - everyone is looking for good big men. We may get lucky this summer with all the free agents, but unless we can entice away LeBron, the Sixers are pretty far from contending for a title.