Presumably a bit of everything. Personal experience is that there will always be some people that inter-marry, which usually works ok when religion is dispensed with. I also know of the opposite, where religion has thrown a real long-term spanner in the works following a death in the family.
The demographics will become more skewed as things stand and it is difficult to argue otherwise. I'm not optimistic that it will be for the better. However good your immediate circumstances are, public opinion will be driven by the headlines.
It would still be better if we were out of Europe with selective immigration, taking the skills we need.