They really ought to change the Johto Dex.
If they won't, then...it'll be bad.
People claim that they follow patterns. People claim that because of FRLG, they won't change HGSS either.
People claim that.
But if you wanted the originals, then why did they add the starters following you around? The Notched-Ear Pichu? Why would they do that?
FireRed and LeafGreen are fundamentally different from HeartGold and SoulSilver. Heck, Red and Blue were a different type of game than Gold and Silver, although they were similar to Ruby, Sapphire, Diamond, and Pearl.
You're wondering how that's true? Listen. Gold and Silver were designed as sequels, not as new games with the same tried-and-true formula. Johto had no Safari Zone, Cycling Road, etc. etc. It had Kanto.
They have to make it different, because most people who play (the little crybaby tots) haven't played FRLG, or haven't in a while. The whole sequel shit won't work. They have to change, the original version just won't flow. It will be different.
And you wonder why I think the new evos will be there? Firstly, having them not able to evolve would be stupid. Say you used a Dusk Stone on Murkrow, but it didn't evolve, just because you didn't have a piece of metal? Does that make sense?
Now, you purists will probably say, "Oh, there won't be a Dusk Stone before the E4, just so we can solve that problem." But you can trade a Dusk Stone from another HGSS. That could happen in FRLG. And things like happiness evolutions, why won't they be able to evolve? They will evolve. Things like Leafeon, Glaceon, Magnezone, and Probopass, which won't evolve without certain specifications - they'll be able to. hey could easily put an Ice or Moss Rock somewhere, and maybe they can have a Mt. Coronet Rock somewhere too, for Magnezone and Probopass.
And you people say, "They have patterns! Things stay the same!" Well, if that's the case, watch me twist your logic against you. In Diamond and Pearl, you were allowed to be traded non-Sinnoh Dex Pokémon before the National Dex, and technically, you could get the National Dex Pre-E4, and use Pal Park and dual-slot insertion and PokéRadar as well (I'm not sure about the last two, but it would make sense). Just because it happened last generation, doesn't mean it'll happen this generation, where it already hasn't happened.
Instead of only showing evidence that proves your point, look at all the evidence. Follow all the patterns, not just ones that aid your cause, or have relations with the current point at hand.
Anyways, onto my interpretation of the Johto Dex.
All the Johto Pokémon and their evolutions make 151.
Then, add those Pokémon that are in every Dex, like Geodude, Machop, and Abra, as well as some of those 3rd and 4th Gen Pokémon that fit that bill as well, like Feebas and Wingull (although I can't think of any 4th Gen ones).
Then, add a few of those Kanto Pokémon that have meaning in the game, like Gastly (Morty) and Bellsprout (Sprout Tower) in as well.
Finally, add a few random 3rd and 4th Gen Pokémon in to finish it off (maybe about ten-fifteen Pokémon, twice the number of random ones in Platinum). These shouldn't be stuff like Salamence, Metagross, and Garchomp, but things like Altaria, Roserade, etc.
And that's a new Johto Dex.