It is not in the wokrs now, nor will it be for a long time.
There are a few reasons why.
1) Because this game is massively large, if you wanted to include all the areas a player can travel. The game could easily take upto 3 discs if all the areas were included, indigo league, orange islands, johto league, and the advance league.
2) You would have to model over 250+ pokemon and set their attacks, blocks, movements, etc. Adding to developement time and much much more.
3) Traveling from area to area would come into question. How would you do it? Would it be like Gameboy games where you travel form place to place. If this was so, then you would have to develope very complex areas and accordingly to do it that way. But this could also get boring going from one area to another (like sailing in wind waker)
4) I'd expect this game to be a massive online game, where there is one world and people travel from one place to another, challenging others online.
This game is not as easy to make. Just look at Pokemon Stadium, it took a whole game just to have battles against eachother. YOu guys are asking for a HUGE MASSIVE WORLD