I assume the OP's question has to do with the banning of AR's as a class (which would include AK's, etc.).
In that case, the fallback position would be something like a Garand. If all semiautos were banned, then you would go to bolt-action milsurps.
If you are investing in guns with an eye to possible future bans, what you invest in depends on whether you think existing guns would be grandfathered, or not. If you think they will be grandfathered, put your money into AR's. If you think there will be no grandfathering, buy milsurps. Or hedge your bets and buy both.