OK, I was off by a year. 2000 and 2001's were the only ones released in circulation. http://en.wikipedia.org/wiki/Sacagawea_dollar
2000 Sacs Whenever I get $1 in change, it's always the 2000-P. Once I got a 2001-P. So it must be true that none of the later dates were ever released into circulation. I also never see the commemorative nickels that were released not too long ago to honor Lewis & Clark.
I see the 2004 and 2005 nickels in circulation all the time around here to the point it's not even a notable occurence anymore. I've met some foreign tourists who were confused by the designs before; had to explain to them that these designs were temporary and still worth five cents. I work at a mall now that seems to attract foreign tourists often, especially this time of the year, sometines this results in some interesting foreign coins mistakenly ending up in US circulation. Anyway, yes, you're correct, Sacagaweas were only released for circulation in 2000 and 2001. Anything later than that was only minted for sake of collectors and rarely makes their way into circulation, but it can happen if anyone wh bought the rolls chooses to just spend some of them. I have found some Kennedy halves from years they weren't released for circulation in circulatrion anyway, so it does happen (including a couple of proofs!).
Not going to happen; the presidential dollar legislation guarantees this will be produced far in excess of demand, and there's just ont enough interest in them anymore as compared to the presidential dollars.