Let's assume all the following (which is completely unrealistic):
- Everyone uses Taproot
- Every channel opening transaction is one-input-one-ouput
- Every transaction being made is a Lightning channel being opened, and no one makes any other type of transaction
- Every block is optimally full
- Everyone only opens a single channel which they keep open forever
Even assuming all that, then at most you can open 9,000 channels per block, meaning it would take 17 years just to let everyone in the world open a single channel. As soon as you consider that obviously some people need to have multiple channels open for Lightning to work, and obviously people will want to close channels, open new ones, top up their channels, and so on, then that number increases exponentially.
if we're working with assumptions, then let's assume that Eltoo lightning gets a soft fork:
- slightly fewer than 9000 channels per block, but far more than 2 participants per channel
- the overhead for adding extra channel participants is negilgible
- Eltoo therefore radically improves the number of people opening channels in a block beyond the 18,000 possible with taproot channels
If "radical" even halves your 17 years figure, and I think it will do far more, then Eltoo will do the job. Considering how fast taproot was activated, we can expect something similar for eltoo (which is now a pretty mature spec with years of technical discussion behind it)