The thing is, as Mirrorball Man points out below, you've set it up so "bloat" = "rules". And errata. Any rules.
While you certainly could define anything past the three core rulebooks "bloat", that isn't really what WotC and a significant portion of their fanbase is worried about.
Additional adventures and additional monsters aren't really the bloat WotC is worried about. More monsters are just more options for the DM to craft adventures with . . . . I've never met a DM who's complained about "too many monster books". Although, towards the end of 3E it did seem that some of the critters in the last few monster books were, well, filler. Specific rules modules aren't serious bloat either, as they are very situational and don't add a ton of weight to the core rules.
Campaign settings aren't exactly bloat, but each individual setting (beyond the Realms) isn't desired by enough folks to make printing books (even e-printing) worthwhile. Greyhawk is awesome, but are there enough folks who would buy the new 5E campaign book to make it worth doing? Probably not.
It's character options that are the serious bloat issue. Character classes, subclasses, feats, weird weapons, backgrounds, spells, and magic items. When you *need* seven books to create the character you want, or have to wade through hundreds of options in an online character generator, that's the bloat problem. It's a bit of a perception issue rather than a reality issue, as you never truly need to purchase all of those options, but perception is reality . . . . if players feel like they need to purchase multiple splats to "keep up", their interest can diminish. Not to mention each splat sells less copy than the one previous.
I also think there is a "core book" bloat issue. The perception that to have a complete D&D collection includes not just the core three, but a Deities & Demigods, Manual of the Planes, Draconomicon, etc, etc . . . that can really be a dash of cold water to somebody interested in the game.
I think we'll get a lot of those products (or, at least, I hope we will), but on a much slower pace with higher quality control and an effort to minimize that perception of "bloat".