Brexit is going to happen, that's pretty much set in stone at this point. They've invoked Art 50 and negotiations are about to begin for the separation, although it'll probably only get serious after their snap election with those in about a month. The UK might rejoin some day in the future, but for now that it's going to happen is a certainty unless Britain themselves changes their minds, which is very unlikely.
Britain already had more favourable terms with the EU than many other member states too.