Re: I think that's a Great Question......
Hackenslash said:
I would say that this question would be best answered by WoTC, as it is they who are making us all buy more "Core Rule" Books without much justification, other than a few minor changes, which in theory could have been published in a "Soft Back, Black and White Supplement"
Well, they do that: it's the SRD, which will be completely updated. So if you only want the new rules, download the SRD, print it, and here you go. You're paying only your time online, some paper and ink/toner for your printer. I can well imagine it that they mark those parts of the SRD they update, so you can just download and print that.
But I'll get the new books: I have the 1st printings of the core rules and there's so much that has been errata'ed, which doesn't show up in the books. Also, my PHB is coming apart.
To the original question:
The core rules will be redone. Other books aren't planned (or they didn't tell us). There are rumors of a revised Psionics Handbook, though.
They will release a Forgotten Realms Player's Guide, a "supplement" to the Forgotten Realms Campaign Setting which will update the FRCS data to 3.5 and incorporate the Epic Rules into the Campaign (and I still hope they'll incorporate some developments from the various novels and maybe modules - including Artemis Enteri's "change").
Then there will be "The Complete Warrior", but that is by all reports no revised Sword & Fist, but a book about combat, with information for all classes (and featuring 75% new material, the rest being taken from former publications and from Dragon Mag).