I don't know what 5 will hold, but from the general atmosphere I've seen from the RPG community, I believe it might fail, no matter what it looks like. Here's why:
Players A, B, and C: I hope they do away with the gamist mechanics. As long 5e has things like "powers", "healing surges", and "retraining", I'll never buy it.
Players D, E, F, and G: I don't care for those things either, but I can live with them. What I hate is eladrin, dragonborn, and the fall of the Realms. If 5e retains these things, it's a no go for me.
Player X: What's wrong with retraining?
Players H, I, J, K, L, M, N, and O: Sure, but I don't want to go back to 3.X either. Some of these things were decent that 4e introduced, although they were implemented poorly, and I'd like 5e to encompass those improvements. And if 5e looks anything like previous editions, including Pathfinder, I won't buy it. If I wanted to play those things, I already have that oppurtunity.
Player X: I asked, what's wrong with retraining? And dragonborn for that matter? The game is called Dungeons and Dragons. A dragon option for PCs seems like a great idea to me.
Players A, B, F, and G: Why wouldn't 5e look similar to previous editions? This is where 4e messed up, by slaughtering too many sacred cows. Too much difference and the game is no longer D&D.
Players B, F, and M: Actually, previous editions are in need of some major improvements. The game is too complex, which is why I developed my own heavy houserules for 3e.
Players E and K: Well, the same for me, but my houserules are based on the better balanced 4e.
Players A, B, and C: 4e may be better balanced, but it's not as stimulationist or flavorful.
Player A: Though I thought eladrin and dragonborn were good editions and should be retained for 5e.
Players D, E, F, and G: What? Heck no?
Player A: You can just ignore them. Besides, previous editions had tons of offshoot races and dragon races.
Players D, E, F, and G: But not in the core!!
Player X: But what about retraining. Also, I like the new Realms. The previous version didn't leave enough room for the PCs to be the stars.
Players K, L, and M: The new realms are fine. But the game isn't too complex, it's too simple. I need bunches of advanced rules.
Players D, E, F, and G: Take that blaspheme back about the Realms!
Players A, K, E, and O: I like advance rules, too. I can build the flavor myself, so that isn't an issue at all for 5e, despite what others want.
Player A: Though it would be nice if they kept the eladrin and dragonborn. Oh, and the tieflings too.
Players B, X, F, and M: Advanced rules are fine, but they shouldn't be in the core. The core should just be the basic game. If 5e is too complex, I promise I won't play it.
Players K, E, N, and P: Why can't they include all the rules in one core. If they wait until a supplement for the "advanced rules", I don't think I can be a part of that.
Player F: If the advanced rules are in the basic book, then there actually isn't a "basic". I can't agree with that direction.
Player Q (based on my Salvageable Innovations from 4e thread): Quick question. Is there anything we can salvage from 4e when moving to 5e.
Player R: Sure, <Feature 1> and < Feature 2>, but surely not <Features 3-100>.
Players D and G: Are you kidding? <Features 1 and 2> are the very reason I can't stand 4e. And <Feature 72> was the one redeeming feature of the edition.
And so on and so forth. My discussions have led me to believe that, if indeed "4th edition was not accepted overall and didn't do as well as the designers thought", it was because of reasons on which everyone disagrees. The same is true of previous editions. Therefore, I think 5e might fail if it is too similar 4e, looks too much like previous editions including Pathfinder, or is different in too significant a way than any of these (and one of these has to be true).
However, there is one way 5e might succeed, no matter what it looks like:
Players A-Z: Ooh, a new edition. [Runs out and buys it. Then runs to the internet/gamestore to complain].
