I will agree for the most part, however I know quite a few that feel burned by how WotC(Hasbro) has handled D&D recently that they don't plan on going back. ...That could change once 5E returns, but there are a lot of bridges that will need to be rebuilt in order for the game to reach its former glory, if it even can.
I see this online sometimes but I think the number of people who will refuse to buy the next version of D&D because they're still mad about the last version is pretty small. I mean logically, if you dropped D&D because you didn't like the direction the company took it, well, you won! they're changing the game back towards what it used to be. I can't think of a better apology than 1)dropping the game they didn't like far earlier than expected and 2) using a lengthy open playtest to design the replacement. People may not like the new version for whatever reason, but that's different than still being mad about 4E.
Plus, these aren't mutually exclusive choices - people can own and play 3E/4E/5E/Pathfinder, 13th Age, and Numenera concurrently if they're interested
Pathfinder on the other hand is starting to face a similar fate I believe in that the game is getting so bloated that it is on the verge of imploding as they continue to expand the rules and eventually will face the need for a second edition.
I agree that it will happen some day but I don't think it will be all that soon. I don't think it makes great sense to release a new edition at the same time the new edition of D&D is coming out. Give it a year or more after Next is officially released and then you might see something. We're only 4 years into this edition of Pathfinder, it can run for a few more.
Numenera may break away from the D&D clone fate because while it has a very fantasy feel to it you can't help but remember it is a sci-fi game as well. Definitely it sits in its own niche at the moment and I would love to see it remain there. Sci-fi or even sci-fantasy has never had a game that equals to D&D as far as staying power or dominance.* Given the figures which can be found at the Kickstarter website and from Monte's admission to the PDF preorder the game is definitely popular, but as you say time will be the biggest factor in whether it remains that way. I would love to see sci-fantasy become its own market niche with Numenera filling the roll of flagship, but can’t help that like sci-fi it will be an area that sees fits and starts a lot.
Numenera is interesting but I think it's too "weird" to have any long term dominance. The kickstarter was big but I think a lot of that was Monte's name on it and once DM's start trying to talk people into playing it I think the road gets a lot tougher. I'd like to see it stick around, and it will at some level, but let's meet back here in 3 years and see what we have : )
*I am making this claim because while there are popular sci-fi games, such as Alternity, Star Frontiers, Star Wars, and Traveler to name a few, none have taken a dominant role as D&D has within that genre/niche market. One could possibly argue Star Wars, though I wouldn’t classify its popularity as being strictly gaming related since it falls into its own dimension of fandom as does all things Star Wars when taken as a whole.
D&D may be the granddaddy of them all, but you have to admit that something about it definitely set it apart as the preferred game by the majority of the fantasy fans in terms of game play over the years, at least until 4e and even then it still commands a large portion of the gaming community in terms of fantasy gaming.
Early on Traveller was pretty dominant, then the company decided to dramatically change up the rules and the setting and it lost a lot of ground - sound familiar? The Rebellion and "The New Era" is pretty much the "4e/Spellplague" of Traveller history. Star Frontiers was pretty popular -it was TSR- but it only lasted about 3 years as a game line. I agree that Star Wars is kind of it's own thing and hard to gauge.
Champions was the big supers game for quite a bit of the 80s and 90s even as Marvel and DC came and went but the company lost steam and Mutants and Masterminds jumped in and took Hero's lunch money and has yet to relinquish it, so change is possible even after a long run.
When you get into science fantasy type weirdness some of it depends on where you draw the lines. Shadowrun might bleed into it and it's pretty popular. Gamma World has had some peaks (and valleys) over the years. Rifts was regularly in those top 10 sales lists in the back of magazines in the 90's though you never hear much about it online thanks to the owner. The 40K RPG's are up there now and if it wasn't split into 5 different lines it might be perceived as more dominant than it seems to be.
13th Age has both a bigger chance and a bigger risk, I think: over the long haul some games ride alongside D&D and do well enough, like C&C. Others get squeezed out by "we could just play D&D" like Palladium Fantasy. Time will tell.
Numenera, despite having "Monte Cook" on the cover, has less of a link to D&D in my mind, partly because of the setting, partly because of the rules, and partly because of the kickstarter. the setting is different enough from standard fantasy that it's necessarily competing with D&D, the rules are not standard d20, and kickstarter backers tend to be invested in a game beyond just financial considerations. That means there will be a vocal, active core of people pushing the game and that should help quite a bit.