Making big changes in a successful franchise is generally bad strategy. It alienates some number of the existing fans and, unless done extremely well, doesn't attract enough new fans to make up for the loss. They have a successful formula. The best strategy is to do exactly what they've been doing - to repeat the formula with a handful of generally carefully planned and well-implemented changes, as warranted.
It's not a coincidence that Pokemon is almost certainly the best, and possibly the only, example of a game franchise that has never put out a really bad game. Virtually every other franchise has put out at least one game that's widely and justifiably regarded as poor-at-best, and usually because they broke from the successful formula, often apparently for no reason other than to change things up and make it different.
There will always be those self-professed fans who want a successful franchise to do some different game. I've always believed that everybody would be better off if they took their desire for some different game and applied it to actually playing some different game. Leave the successful series as they are - that's why they're successful. Those who think it should be something else are welcome to go play something else.
That's not to say that nothing should change, of course. GF has a great history of making necessary changes, and virtually all of them have benefited the franchise. The introduction of Steel and Dark and the splitting of the defense stats in Gen II went a long way toward fixing the terrible imbalance of Gen I, and the physical/special split of Gen IV was a brilliant change that made a large number of old and new pokemon and strategies viable. Changes like that - carefully thought-out and well executed improvements - should certainly continue. I'm not sure how many more of them there are though.
Yeah - some of the types seem unbalanced, but, to me, they aren't really unjustifiably so. It made sense to me when I first played the games, and still does, that, for instance, Steel and Dragon and Rock are relatively strong types and Grass and Psychic and Ice are relatively weak. And even with those, the ways in which and the things to which they're strong or weak make sense. I would expect steel to hold up to most things but to be in danger from fire and from brute force. I would expect psychics to be generally physically weak but able to hand out some fairly substantial damage if and when possible. I would expect ice to be dangerous but not really tough to deal with. I would expect grass to be largely unable to hurt others but very resilient, unless burnt, frozen or poisoned. And so on.
There are a few things I kick around as possible good ideas, but I'm not convinced that they're genuinely good. I don't know enough, even now, about all the complexities of the game balance to be sure. The change I wanted the most, and dreamed about for years, was the physical/special split, and I got that. To their credit, GF generally hasn't tossed aside the successful parts of the games in the name of change for change's sake (unlike most other game franchises), so I mostly just trust them to get on with it, and they mostly do.
That said, it bothers me every time I think about Ledian's 35 base attack...