As far as I understand it, segwit will enable the lightning network to function. Bitcoin is all about enduring solutions to problems, not temporary ones link increasing block size. As Andreas says, if you make a 2mb block we'll fill it. If you make a 4x block, we'll fill it. Block size isn't the problem as much as total throughput. If I'm not mistaken, LN will enable tens of millions of transactions per second.