It's certainly possible.  Some articles are already speculating that LN might evolve to be more of a "gateway" to make other layers interoperable. 

I'm reluctant to accept the notion that we should be introducing more custodial control, though.  The whole idea here is that we're meant to be cutting down on that sort of thing and removing the need to trust middlemen.  But I'm certain there will always be a non-custodial option for those who wish to take responsibility and maintain their monetary sovereignty.  Basically, there will be something for everyone.  However you want to manage your wealth, there should be a way to do it.