Look at how cheap the fees in the L2. How can we need L3 if there are so many L2s available in the market? Are you sure those blockchains will be invaded by human then they will be congested? The list are containing a few L2s. There have been so many new L2s still unlisted from that list like manta or even blast.
L3 is not even needed. It is being created as the purpose of making money only. There's no urgentcy to create L3 blockchain. L3 is only for grab your money. L2s are enough.
Obviously L3s are not needed yet because the masses actually barely 'use' crypto to do swaps and DeFi and such; because most people are just in the Coinbase's or Binance's of the world.
But if we expect the masses to actually use on-chain crypto? These fees would easily not hold and we're definitely going to need L3s.