Some of the stuff from the splatbooks (a few feats, a couple of spells) made it into the 3.5 PHB as well.
But, Jester's got it right. The stuff (parts of it, some of it) will appear in future books like the Complete Warrior's blah blah blah.....(or so that's what I heard as well). But, yeah- I did hear they will not be updating/re-releasing the splatbooks (other than like what Jester said above).