"Rebuilding" isn't a one season process, and it's not something done in a single summer. Danny is a very smart guy, and he's been preparing for the loss of the older guys already.
Shaq has already said he's retiring after next season, and he may even do it sooner, as the amount he can contribute has been painfully exposed this year.
KG, Paul and Ray can still play extremely well, and regaining their chemistry would be a difficult thing.
I think the attention area is mainly the bench and a "true" Center ... with those positions strengthened, we can still easily contend with the Big Three.
As for the future beyond that, rest assured management is already planning for it.