It does not matter if SA:MP players make the majority of the players in the Argonath community, there are still vast amounts of players who play on MTA:VC, VC:MP and MTA:SA and appriciate the resources used to run these servers. And they want to continue playing on these servers.
What is your exact reason for wanting the community to be SA:MP only, you say its a great idea but expand on this, you gain the most of the negative comments towards you from SA:MP players and now you want the community to be SA:MP only?

Sure San Andreas will last longer then Vice City, this is common sense as Vice City is a older game then San Andreas, but this does not mean its finished yet, there is plenty more potential to come from VC:MP client as well as MTA:SA client, progress may be slow for MTA:SA but there is great potential.