Dude, those supplements are gonna have supplements, and they'll have wee little supplements of their own. I done churned that treadmill, so I know whereof I speak.
In some ways I think that's a good thing. The 4E emphasis is on having everything spelled out in the rules, so a book of more rules options provides you with more flexible choices in play. The other day I played 4E with my son quite successfully by letting him just describe what he wanted to do & then as DM I decided how to use the rules to achieve it. He didn't interact with any of the mechanics of the game beyond rolling to hit, and I found it worked quite well in producing an old-school "imagine the hell out of it" experience, very different than any 4E game I've played with adults when we tend to interact almost entirely with the rules & almost never use the imagined scene to decide what's possible or what happens next.
The positive side of this re: supplements is that I wouldn't have been nearly as confident in adjucating Javi's "nature elf" description if I didn't have the druid class we'd written up for Forgotten Heroes, or if that class's mechanics didn't synch as well with the kind of vine powers he came up with. The negative side is that I think each time you define something with rules, it fosters the impression that you need rules to do it, which is the opposite of old-school. But at this point I'm doing no worse than nailing in a coffin; the DIY rules are there on DMG p. 42 for folks who want to use 'em, but there's no money in that.
