I guess it all depends on the use the network will have. Right now we have low fees again, because there are no spam attacks going, and most users don't really do anything with their coins. The fees problem was greatly caused by exchanges like coinbase and gemini, but they seem to be finally correcting the problem by adoptiing segwit and batching their transactions. So for the time being, I think we will have no problems with fees.
In the long run, and if BTC starts getting the support from merchants again, and people start using it, then of course it wont be enough, but that was never the point. Segwit is suppose to help in that matter, but it's "true" purpose was to solve the malleability problem, so that LN would work properly (don't know the exact technical details, but I do know it's related).