You don't expect EU to collapse because the UK leaves do you?
If you want changes in your lifetime, better be on the inside making those changes.
There's no effective change that can be waged against the EU from the inside which is the entire point, which is circular with see above. Can't even get the Germans to stop inviting people to show up on their doorstep rather than make the refugee camps in Turkey better places to live in and sort the Syria situation out. Hell the EU is making no effort to sort Iraq's IS population where we're invited explicitly so..
Hence we're better of out. It's not changing either way but the UK can be a freer and richer place where citizens can effect change. Sure can't as EU members.