I can't see recent developments affecting skilled professionals. At the worst there may be some extra paperwork to navigate through that didn't exist before but I doubt that it will be a complex issue.
There are many Europeans who live and work for UK airlines and BA at first glance seems to employ a sizeable number of Europeans, relative to the number of Brits who are employed at other European flag carriers. I suspect BA and many other UK airlines will not be changing their recruitment policy soon.
If you want an existing example of diversity and free and open borders within the aviation industry within Europe, look no further than the UK. To think that someone from the other side of the world with the right to live and work within Europe will suddenly be more employable than someone from the UK is totally unrealistic.