I've said it before and I'll repeat myself; we have to wait for Pryce. He's the key to everything. If we can battle him right before Morty, then all hopes of a higher-leveled E4 are gone. If you have to battle Jasmine before him, then the E4 is "saved".
Do not expect anything from the rosters anymore, though. Four out of eight gym leaders didn't have a change, so it's best to keep your hopes down to not get disappointed.
You mean "right after Morty", right? Because you couldn't even enter Mahogany Gym until after you beat Team Rocket in their hideout. Which first required battling the Red Gyarados. Which required Surf. Which required the Fog Badge. Still, it comes to almost the same thing.\
Either way, I'm fairly optimistic that Gamefreak learned from their mistake and had the sense to block off Mahogany and/or Lake of Rage until you had the Mineral and Storm badges. The simplest and most sensible way I can think of is having the RageCandybar salesman block the entrance to Mahogany Town until you have 6 badges, then he takes his usual post at the other end of town. But I won't go off onto that now. This is neither the time nor the thread.
Anyway, to those who are complaining about the rosters, although I was coming close to being one of them, especially on the subject of Morty, it's not a big deal. First, we only got confirmation on four out of SIXTEEN Gym Leaders. And then there's the Elite 4, and Serebii's confirmed that Red's roster's changed somewhat. And even so, what's the worst that can come of all the gym leaders' rosters being unchanged in species?
Jasmine: Magnemite, Magnemite, Steelix.
This wouldn't be too bad. Granted, I'm hoping that Magnemite #2 is evolved in this, but I'm not betting on it. There's also room for Skarmory, but I just can't see it somehow.
Chuck: Primeape, Poliwrath.
Using Poliwrath in a fighting gym isn't just good, it's genius. And Primeape is still cool. In fact, if memory serves, GSC didn't introduce too much in the way of new fighting types, save for Tyrogue and Hitmontop.
Pryce: Seel, Dewgong, Piloswine.
OK, here I had a bit of a problem. Seel not only reeks of repetitiveness, given Pryce's Dewgong, but isn't even an Ice-type. And there was plenty of room for Lapras, Sneasel, or even Delibird. But even so, if this doesn't change, I won't complain. Why? Because it is one of three Pokemon belonging to one Gym Leader out of SIXTEEN. It isn't even his main Pokemon. It is insignificant.
Clair: 3 Dragonair and a Kingdra.
The Dragonair trio is repetitive, but this is excusable given GSC's lack of Dragon-types. THe only other Dragon-types Clair didn't use were Dratini (too weak for the last gym before the E4), and Dragonite (and Lance's were underleveled as it is!). I won't complain at all if they don't change this- in fact, I'll be very surprised if they DO find a good way to change this.
So you see? Even if the rest of the gym leaders in Johto have unchanged rosters, it's really no reason to complain. In fact, they only made ONE roster change in FR/LG, and that was turning Giovanni's Rhydon into a second Rhyhorn.
Now, if the KANTO gym leaders have the same rosters, on the other hand, that'll give me a bit to grumble over. That's assuming you get the National Dex BEFORE fighting the Kanto Gym Leaders, that is. If you don't, then, well, there's nothing much what that can be done.