Jeffrey, I can add a number of things to my previous post on this subject. As you wrote, chess has the advantage of a strong tradition. For many lesser variants of popular card games, a lot of people prefer playing well established games that everyone already knows how to play, when sitting down face to face, so it's not a question there of lacking equipment (a deck of cards), as I think Fergus once alluded to long ago. Unless there are relatively few rule differences from chess, a chess variant faces a similar hurdle of familiarity alone to overcome, on its way to ever obtaining widespread acceptance (for everyday face to face contests, at least).

One of the things that may well have made chess so popular is simply the beauty of the pieces for a physical set. Shogi, for example, may lack this advantage (at least in Western eyes), besides games of it tending to last somewhat longer than chess on average, in terms of moves, afaik. Crazyhouse has the excitement of shogi drops and attacking, as well as somewhat retaining the beautiful physical pieces to play with. I don't know how long the average game lasts though, and it may not be strategic enough to encourage a large percentage of chess fans to ever switch over, even if they've already ever retired chess. Crazyhouse has been out there a while, so presumably it's reasonably well tested, yet it still accounts for less than 1% of all games played on that chess server I wrote of in my previous post, in spite of the fact that it's quite a popular chess variant currently. I once noticed someone's suggestion of using Chess960 style random setups for Crazyhouse, to avoid any opening theory developing, but this might have some of the same disavantages as for Chess960 that I wrote of in my prior post (i.e. some setups perhaps favouring White, at least).

I actually prefer a fixed start position for the setup of a given variant if possible, given that merchandising and movie scenes can be aided by this, not to mention books on opening theory and the attraction of a decorative set in one's home with pieces already set upon the board in an orderly fashion. I'm also not too averse to a certain amount of opening theory developing over time. That's though I've heard that's actually getting to be a concern for Shogi, which otherwise seems almost an ideal next chess in many ways - not least, the low draw rate in elite play even, and a fixed setup may make any potential next chess not an 'Immortal Game' (i.e. it may eventually ought to be abandoned/replaced if a dominant variant is deemed desirable or not). As I wrote earlier, a way to avoid this is e.g. Chess960 style shuffling of the setup, or using card decks, as much as I don't entirely like either means, at the moment at least. However, nothing as seemingly perfect as chess once seemed to be (to chess players, at least) may ever be possible to find. My own Sac Chess variant, for example, has a lot of possible pros as well as cons in my own eyes, and when people have commented on it it's often been to wonder about possible cons. The range of good relatively early opening moves for a game of it might actually turn out to be significantly lower than for chess, but as reserve pieces are brought into play from the rear, the later stage opening possibilities hopefully hugely multiply. That's without any Chess960 style shuffling of the setup being tried.

One thing that might happen at some point in time is that FIDE or someone else may get a committee to study many chess variants, if it looks like chess is getting to the point where it needs replacing 'officially', at least for big events. I hope that The Chess Variant Pages website, or some variation of it, will still be around at that point, with all of its diverse chess variants to consider as candidates for the next chess, besides variants that might be found elsewhere, say on the internet. I'd note that not all chess variants were intended to be practical or serve as a possible next chess, however.