@aubert last like I checked we have so many layer 1 projects and the number is more than layer 2 projects, also layer 2 projects handles transactions more than layer 1, you said they might not do well in future? With Arbitrum and few others that looks more promising than optimism I doubt layer 2 will fail, all you got to do is compare, the answer is a there.
Arbitrum and Optimism are 2 projects that I want to bet on, they all have the same potential. I don't think layer2 will fail, it solves a lot of problems for layer1 and ethereum's upgrade doesn't affect layer2 development at all. Alternatively, you can also consider investing in Polygon, it is sidechain rather than pure layer2 but very promising and solves similar problems as Arbitrum and Optimism.