Here is why I am not looking forward to (the eventually inevitable) 4th Edition. . .
Back in 1999 I remember a lot of people being wary of the coming of 3e, and a lot of people saying they weren't going to leave 2nd Edition behind. However, things are different now.
The AD&D 2e our gaming group (and most groups I knew) was playing was houseruled almost beyond recognition. AD&D 2e was barely meeting our needs for a fantasy RPG, it wasn't really meeting them at all, but the learning curve of learning a lesser known RPG instead combined with the rarity of players made switching impractical. A number of players had refused to switch to 2nd Edition from 1st Edition and 1e AD&D groups were still around, because to many 1e players there was no real improvement 2e offered over 1e.
The switch to 3.5 from 3.0 was mostly trivial, nowhere near as huge as the 2e to 3e shift. Mostly the changes were understandable, like eliminating front-loading in classes like Ranger (it was clear in the making of 3.0 they didn't anticipate as much multiclassing as would happen), or to fix "broken" spells.
Now, with 3.5 we have a set of rules which doesn't have any. There are tiny rules-fixes like swift actions that can be added on, but nothing worthy of a whole new edition. A large change to a new edition doesn't seem needed, it doesn't feel like it could honestly make things better.
A 4th Edition would have to be an incredible game that was clearly superior to 3.5 for me to switch over.