The earth and the universe are riddled with evidence, and discoveries will be made that will be verified by evidence that exists long before we discover a fitting theory. Will it be low hanging fruit? I don't know, but far in the future those discoveries will also seem obvious to people living in that future. But the point is that, all of the evidence we need to make a new discovery is already out there, we just have to conjecture a new theory before we can make use of it, before we know what even to look for.