I wouldn't hold your breath, granted it only takes one stroke of dumb luck to change everything.
The Lakers don't have to do much to hold up their end of the deal. They're a double whammy; they're an attractive team for players of all types because they're constant contenders, they've won 10 titles since 1980 and they've been in the finals essentially every other year, and their home city is probably the most desirable one in the country. Not too long after Kobe's finished they'll draft another Kobe or Magic and be right back at it. Success will come to them, unless Jim Buss completely shits the bed.
The Celtics on the other hand are basically back in 1993 now. Garnett and Pierce are old. Rondo's talented but he plays up and down to his competition and doesn't make his teammates better, and now that he ripped his ACL his trade value is gone. We don't have any future franchise players on the roster, nor do we have any means of getting one outside of the draft. Boston isn't a destination on the NBA map, it's cold, it's in the shadow of New York, and it still has the racist tag. When Red built the Russell dynasty, he was well ahead of his time in a league filled with boneheads. When that was over he still had Havlicek (franchise caliber player), and was able to draft Cowens to go with him, and got two titles out of that in the 70s. In the late 70s when the Celtics were tubgirling, Red made an enormous gamble by drafting Bird's rights while he was still in college. Once the Bird era was over, the Celtics stalled because the rest of the league had finally caught up. Everyone else was as smart as the Celtics, if not smarter (due to Red taking a back seat), and all the loopholes were closed.
We could get back on top by throwing away next season for a strong draft class, but the owners won't have that because odds are they're getting ready to sell the team. It's hard to sell a basement dweller when they haven't had prolonged success since 1990 and don't play in NY, LA, Chicago, Dallas, or Miami. So we'll be riding Pierce and Garnett until they expire, Rondo will 'lead' the team to a bunch of 29 win seasons, and barring a miracle it'll probably be at least a decade before we're relevant again.