Given the evidence that the move-based evolutions will be in the Johto dex, plus other stuffs I made up in my mind, I will try and predict the gym leader lineups.
Falkner:
Pidgey lv. 8
Pidgeotto lv. 10
(I doubt they'd bump up the levels TOO much. Remember, in this game, beating the Elite 4 is only half the game, hence the underleveling. Also, prize will be either Pluck or Aerial Ace)
Bugsy:
Metapod lv. 14
Kakuna lv. 14
Scyther lv. 15
(I just want them to keep this as is. A Gym Leader using Metapod and Kakuna is pure lulz, plus balances out the fact that he uses a frickin' Scyther. Prize will probably be U-Turn)
Whitney:
Aipom lv. 19
Clefairy lv. 19
Miltank lv. 20
(Anyone who battled Whitney in G/S/C knows what I mean when I say that Ambipom AND Miltank on her team would be beyond overkill. Hence, the Aipom. For similar reasons, the Miltank stays at level 20. It was hard enough to take out that thing, they do NOT need to bump up her level! Prize will likely remain Attract. Miltank, unfortunately, will probably retain Rollout)
Morty:
Gastly lv. 23
Haunter lv. 24
Misdreavus lv. 24
Gengar lv. 25
(They introduced the only Generation II ghost, and gave the Generation II ghost gym leader everything BUT. AND a second Haunter, to boot! No. If they have any sense (and based on that remixed music, they do!), they'll axe Haunter #2 and bring in Misdreavus. I'll bet anything they'll keep Shadow Ball as the prize)
Jasmine:
Magnemite lv. 32
Magneton lv. 33
Steelix lv. 35
(I just couldn't find a spot to insert Scizor or Foretress anywhere. Best I could do is evolve Magnemite #2. Prize will either remain Iron Tail, or change to Gyro Ball or Flash Cannon)
Chuck:
Primeape lv. 34
Hitmontop lv. 34
Poliwrath lv. 36
(No Machoke, despite lack of DynamicPunch TM. Gamefreak will probably spam innaccurate and powerful moves with No Guard if they gave the dude a Machoke. Plus, almost nobody used Hitmontop in Johto, and this is a good opportunity. Prize might be either Focus Punch or Brick Break)
Pryce:
Dewgong lv. 35
Sneasel lv. 36
Piloswine/Mamoswine lv. 37
(Seel AND Dewgong made little sense, especially given the new ice-types Johto introduced. Plus, Sneasel is just cool. And as for Piloswine, I just can't imagine it evolving, but I have this feeling they'll do it anyway. Prize will probably be Blizzard or Avalanche)
Claire:
Dratini lv. 36
Seadra lv. 37
Dragonair lv. 37
Kingdra lv. 40
(That's as much variety as I can try to inject in Claire's team, unfortunately. Hey, anything's better than the Dragonair trio, eh? Prize will probably be Dragon Pulse, but they'll lose the joke about Claire's breath. That made me laugh every time)
Will:
Xatu lv. 41
Slowking lv. 42
Jynx lv. 42
Exeggutor lv. 42
Xatu lv. 43
(Upped the levels slightly, and gave him a Slowking. It just made more sense to me)
Bruno:
Steelix lv. 42
Hitmonlee lv. 43
Hitmonchan lv. 43
Hitmontop lv. 43
Machamp lv. 44
(I don't believe his Onix was evolved in G/S/C, and well, this is Johto, even if the Elite 4 is technically in Kanto)
Koga:
Ariados lv. 44
Crobat lv. 45
Arbok lv. 45
Qwilfish lv. 45
Weezing lv. 46
(He's supposed to be a poison trainer, and he had a Foretress?! I could give him lessons on Poison-types. ANd two bug/poisons? No. Replaced Foretress, Venomoth and Muk with Arbok, Qwilfish, and Weezing. Better. Much)
Karen:
Murkrow lv. 46
Sneasel lv. 47
Umbreon lv. 47
Houndoom lv. 47
Tyranitar lv. 48
(Underleveled, shmunderleveled. T-tar is a surefire way to add a challenge to this Elite 4, while retaining the slight underleveling. Also keeps to the Dark-type theme)
Lance:
Gyarados lv. 48
Kingdra lv. 49
Charizard lv. 50
Dragonair lv. 50
Aerodactyl lv. 51
Dragonite lv. 53
(Again, the underleveling is due to the fact that in this game, the Elite 4 is merely the midpoint of the game. I try to stay true to that, and add a tad of variety to Lance's team. Unfortunately, Johto's severe lack of Dragon-types hinders this considerably. Still, I think I did OK)
Lt. Surge:
Lanturn lv. 55
Raichu lv. 56
Rotom lv. 56
Magnezone lv. 56
Electivire lv. 57
(I'm assuming that Kanto=National Dex here, obviously. Prize=Thunder)
Sabrina:
Wobbuffet lv. 57
Slowbro lv. 58
Bronzong lv. 58
Xatu lv. 58
Alakazam lv. 59
(Yeah, yeah, Wobbuffet is cheap, blah blah blah. Do you want the second half of the game to be too easy or something?)
Misty:
Togekiss lv. 58
Qwilfish lv. 59
Bibarel lv. 59
Lapras lv. 59
Starmie lv. 60
(Yes, I have a thing about Qwilfish, so sue me)
Janine:
Crobat lv. 55
Qwilfish lv. 56
Arbok lv. 56
Muk lv. 56
Weezing lv. 57
(Again, the thing with Qwilfish. Plus, Arbok and Weezing are awesome, and do not deny it!)
Brock:
Kabutops lv. 58
Omastar lv. 58
Golem lv. 59
Sudowoodo lv. 59
Rhyperior lv. 60
(Rhyperior is almost a given, really)
Blaine:
Magcargo lv. 59
Ninetales lv. 59
Infernape lv. 60
Camerupt lv. 60
Magmortar lv. 61
Blue/Green (whatever they decide to do)
Pidgeot lv. 60
Rhyperior lv. 60
Alakazam lv. 60
Gyarados lv. 61 (Blastoise if your starter was Cyndaquil)
Exeggutor lv. 61 (Venusaur if your starter was Totodile)
Arcanine lv. 61 (Charizard if your starter was Chikorita)
(Other than Rhyperior, what's to change? I thought the whole starter thing was a nice touch)
Red:
Pikachu lv. 91 (holding Light Ball, take THAT!)
Espeon lv. 88
Snorlax lv. 89
Venusaur lv. 90
Charizard lv. 90
Blastoise lv. 90
(Now THAT'S a final battle!)