I never realized Jon and El-ron had exp with 4th ed! That's pretty cool. I only have limited play time with it from the few Encounters sessions I attended, but I can understand your complaints. I think as far as exploration not being emphasized, I figure that's something that a DM would handle more than the ruleset. You're right that the game is really built around those encounters/set-pieces, but they made encounters-on-the-fly very easy to whip up, so I bet a fun DM could have made stuff feel a bit more organic and open-worldy. Worldy!
My fear of a fan-based D&D 5th Ed is that it'll be the 2nd coming of Pathfinder which is pretty unappealing to me. Mind you, I've never actually PLAYED Pathfinder, but glimpses into that weird fanatical d20 sub culture are such a turn off, I hope the fans involvement is more PR than anything else.