That 8 mb increase every 2 year model would still LN to be able to cope with the amount of transactions needed to compete against the big electronic payment players. Mastercard, Visa, Western Union... they still can move a lot more transactions per second than BTC with a way higher blocksize. So Gavin and Maxwell need to start working together because both visions are needed to reach something that can be scalable for the next decades. I wish we wouldn't have to resort to things like LN and run everything nicely inside the blockchain but I guess that isn't possible.
Well since the lightening network isn't full deployed yet the argument can be made that an increase in blocksize now will help with the number of transactions now and then the LN can aide that process in the future. Also an 8MB cap doesn't mean that each block has to be a full 8MB. If we get to 16MB blocks before LN is in full deployment and then LN becomes fully deployed the cap can still be 16MB, but maybe the actual blocksize will go back down to 1MB/block actually being used.