Just read a great couple of articles on the salary cap situation and basically, it seems that moving Garnett or Pierce is not something that helps much..
To me the best option seemes to bring them back and hope Rondo, Sullinger, Green and Bradley improve enough to compensate for their decline and start the rebuild the following year.
Basically in a nutshell the logic works like this. Even if we get rid of both Pierce and KG Through waivers, retirement, or amnesting one of them and everything goes right like KG agrees to file retirement papers (he could forgo that and screw us badly) The most we can realistically do is to get 27 million off the books and that is if EVERYTHING goes right. BUT That still leave a team salary of about 49 million. So realistically we could get a free agent in the 9 to 10 million range. Not enough to rebuild.
My understanding is all of that looks better in the following year so the rebuild will probably be on the fly until then.