What are the chances that the moves will change in the future so much so that the ideal movesets will change?

I'd be surprised if I saw TM-like usable items for alternative moves, I personally transfer bad moveset pokemons even if they have great IVs, this all come down to if you are patient enough or not , in this case being an impatient person I quickly get rid of em, I know that's bad but I can't help

Probably depends on how 'rare' something is...I have a lot of eevees and growlithes here so I don't worry or feel bad for those if they get transferred since I don't have the space. But for stuff I rarely see, I'd hesitate to transfer any of them (like my Chanseys...good to prestige too usually).