Well transaction scaling, lightning and other solutions including custodial and other solutions that will come along will probably be enough. Custodial might be ok for a few dollars. The biggest problem might be ownership scaling, if fees get too high many people won't be able to use base chain. For that i think Fedimint might be a better option than sidechains, bc at least i can choose who to trust with my keys, can be some friends of mine, or some known bitcoiners. Otherwise, only increasing the blocksize, which should be done imo in the future if there is demand.