I'd love for them to go the multiple earths route in future movies. The DC tv shows (Arrow, Flash) have done multiple earths really well, so I imagine Marvel could do it even better.
Not only would that be a way to get newly acquired characters into the MCU, but it would also give great fodder for future standalone movies. We could get some alternate-earth versions of characters as either heroes or villains. It could also be a great way to get the original actors back for future cameos for any that might get killed off.