The first question, which comes from Ben Weiner, delves into Boston's off-season moves and potential alternatives while also questioning what the Celtics' next move should be. (I'm paraphrasing because what Ben actually wrote was a bit lengthy, but I encourage everyone to look at it on my Bulletin Board; it's well thought out, insightful and provides interesting alternatives to the Celtics' actual moves).
Answer: The justification for every past Celtics' move was this: our best chance at winning a title is this year, so let's put all of our eggs in that basket. While making the moves you suggest (which, for those of you who did not read the original question, results in a best-case roster of Rondo, Bradley, Pierce, Garnett, Jefferson/Howard/Bynum, Terry, Sullinger, Jones III, Moore, and three other possible players playing at the mid-level exception or the veteran's minimum) would help the Celtics in the future, it wouldn't guarantee them a title now or later, especially considering the one major "if" on that roster—the center. I would like to think that an elite center would come to Boston, but we can't ignore the fact that, for one reason or another, Boston hasn't exactly been the most attractive destination for free agents.
It is unlikely that Howard or Bynum would ever come to Boston. Meanwhile, nearly all lesser teams would be willing to overpay for Big Al. And without one of the big-name centers on this hypothetical roster, the 2014 Celtics drop out of contention.
With the moves the Celtics did make, they are still in serious contention for at least this season.
Though one of the implications of the Celtics active offseason is that, in certain ways, it ties their hands for future moves—which makes the answer to your original question of the Celtics next move more difficult to answer. Ideally, they will add a legitimate center, but that may be hard to do with the lack of cap space. Perhaps the only way they could do it would be through a trade involving some combination of either Bass or Sullinger along with Lee or Barbosa. But that move would have to take place after the season.
So, for now, it is unlikely that we will see any more moves from the Celtics.