I think the Spurs have a decent chance to add 1 or 2 more. The key is health and improvement. The big three are set and if Tim remains healthy they have a chance over the next three years. However, Bruce is very important to the team and is nearing the twilight of his career ( so far he hasn't showed signs of slowing but it is inevitible) plus the Spurs BOTD (big other than Duncan) is a concern, as has been discussed on ocaision here. If one ofthe overseas "farm" players (Scola, Javtokas, Ian etc) works out sooner as opposed to later (be it in a trade or actual play) I will be more confident.
I agree Mamis window is very short and KG's team has taken a step back,
Don't count out Detroit, they are not that old and came very close to winning two in a row and AT THE MOMENT the best team in the NBA.