Bedrockgames
I post in the voice of Christopher Walken
I don't understand exactly how you can discuss what's good for the game without talking about what's good for individual groups and players.
As far as I can tell, the most relevant data we have is people's buying/playing habits.
Currently, people are buying, in varying perentages, 4e, 3e/Pathfinder, and older D&D/retroclones, which represent at least 3, if not more, different rules frameworks for creating the D&D experience.
So that's what's good for D&D. That's what's meeting the audience's needs.
I can't help but think the phrase "what's good for D&D" really means is "what's good for me and way I like to play D&D".
It's an implied call not for a change in the official rules, but for a change in what the D&D audience wants from the rules (which at this point includes several fairly divergent, if not contradictory, things).
We already know what's good for the game, using the only meaningful metric; it's what we're purchasing, supporting and most importantly, playing right now.
I would broaden this to say the health of the table top RPG hobby as a whole is what matters. Even if the brand D&D completely dies the hobby can continue. Even if fantasy RPGs go extinct for some reason (or just pass out of fasion), so long as people are still playing games like Traveller and Call of Cthulu, that is all that matters.
But I also think it is fair to ponder whether a more broadly popular game (one that cut across the pathfinder/4e divide bringing everyone to the table) would make the hobby healthier. Personally I don't know. I think it can definitely be good for the hobby for the majority of players to share a common set of mechanics and assumptions, but this can also drive away potential players who want something different.
Obviously in terms of profit, the people making D&D want the biggest share of the market possible. I think there is plenty of room for niche products. But if I own D&D, I probably don't want it to appeal to a narrow band of gamers. I want it to appeal to as many fantasy table top rpg fans as possible. But I am not sure whether you can expand the band now that the hobby has been fragmented between 4E, 3E, Pathfinder, retro-clones etc. And I tend to think the fragmenting is better for the hobby even if it hurts companies trying to be the major player. It kind of reminds me of the pre-d20 days, when you actually had gaming options.