Earlier quoted context omitted.
The point the article is trying to make wrt immigration is that when the UK leaves the EU, it will also leave the free movement of workers zone, making it harder to attract immigrants, regardless of how London feels about them.
Immigration system for skilled workers is not going to change. If the UK actually does leave the EU, they'll replace EU rules of skilled immigration with something similar. The UK is a knowledge economy, it will always be open to skilled immigrants. Yet people actually believe that the UK will close down all immigration. It's absurd.
There's a tsunami of red tape heading our way both in terms of visa regulations and in many other areas where EU and UK regulations are going to start to diverge.
Unless they quickly agree on Brexit in name only we will probably move into the EU, possibly to Scotland if they become independent.