Pokémon doesn't get planned like that. People give them money then they make more.
What about Munna that a Hiker talked about in generation 1 on route 10? Munna had to wait four more generations to be released.
Even if that was a reference to a real design and said design resembled Munna in any way, that doesn't mean they planned to put it in a future game. Heck, when Red and Green were released they probably didn't even know it would sell enough to spawn one sequel, let alone 6 gens.
Actually they didn't even know if they were going to be able to release gen 1 till they got lucky with Yoshi. They used profits from that to finish making pokemon which they had no clue what would happen.