My guess is that British Vogue will just fall under Anna Wintour's complete control, and unfortunately morph into an after-thought like what Vogue France and Vogue Italia have become. The magazine may be still a priority given its current status but I'm doubtful for it's future with Enninful out.
Condé could install someone at the helm of British Vogue who would have some experience in dealing with the Euro editions - like Vanessa Kingori. I have no doubt in my mind Enninful is rooting for Kingori and Sarah Harris as his replacement.
I'm still not convinced a Vogue Europe will come to fruition, like rumors have been suggesting for a number of months. Not sure how a Vogue Europe would work... when there would be a Vogue Portugal and so forth floating around. Unless, however, Condé Nast were to revoke all the licensing agreements with the likes of Vogue Poland which I doubt.
It's all just so up in the air at the present moment with tons of uncertainty...