I think things like Fedimint will become necessary for the average user - lightning payments can tie it all together but if thousands of users are able to make use of a single channel, the scaling really takes off. Whether that's through a side chain with a lightning bridge, chaumian e-cash based federation, or something else remains to be seen. The key is to minimize trust to the maximal extent possible, and there are multiple approaches. What I would prefer and what the market coalesces around may be wildly different, so it's all highly speculative.