Re: For how long will the MCU go?
The MCU will keep going for as long as the money keeps flowing in, it's as simple as that.
Even in the case of Bond, I don't think that it necessarily had to be rebooted, it was just a decision that was settled upon.
The best way to keep things fresh is to rotate the active lineup of characters. My only hope is that quality isn't sacrificed for the sake of keeping the factory alive. People like Feige will prevent that somewhat, which is why I always worry when it comes time for someone like him to step down.