My "fixed" 3.5 has houserules from all kinds of sources.
I run almost pure RAW, using just the PHB, DMG, Deities & Demigods, MM1-3, Living Greyhawk and Fiend Folio.
The only "additional" rules we have are:
1) Selected feats from the Net Book of Feats -- player asks, DM reviews & allows.
2) Unearthed Arcana rules allowing stacking of Divine Caster Levels from different Divine casting classes + same rule for Arcane Caster Level.
3) House rules on Rangers to allow dropping class features like Favored Enemy and animal companion that don't directly related to the "outdoor fighter with skills" idea, with some of the alternative choices based on Pathfinder.
4) Leveling up allows for limited "editing" of old character build choices (a rule from UA or PHB II).
5) House rule that everyone starts at 1st level, or by taking over an NPC. No building a high-level PC. Related house rule that a Warrior NPC can "convert" old Warrior levels to Fighter levels on gaining a level as a PC.
It's got a chase system (mine is borrowed from Five Fingers; written by Wolfgang Baur.)
I've never seen good rules for chases, so I may need to track this down.
But the point, I think, is that WotC recognizes that there's a lot of folks that never stopped playing 3.5, and also didn't necessarily migrate to Pathfinder or any other system. While maybe reprints of books these guys probably already have isn't the best way to sell to them again, I dunno, maybe it is a good way to reach out to them. One way or another, I'm sure WotC wants to reach them again.
Some of my players have joined since 3.5e went out of print. It would be nice to get new books for them.