Oh, MAN! That's right, you're in the UK.
Well, for what it's worth, I seriously doubt anything official will be announced right now. It's almost 5:30pm in Hollywood right now; the suits are all stuck in traffic on their way home.
I AM thinking Friday is a distinct possibility however - maybe even Saturday - and here's why. It is my belief that Warners is going to want to make a BIG deal about this announcement. They're going to call a press conference and have Dan Lin and George Miller there. Alan Horn might also be present. They
might also want to have the big three there for star power - the actors cast for Superman, Batman and Wonder Woman. Ryan Reynolds being such a huge fan favorite might be requested too - if he's cast of course.
Welling is currently shooting SV in Vancouver, so he can't just take off for an hour in order to be present, and his casting would be a HUGE deal if it happens. So Warners might want to wait till the weekend or the days that bookend it (Friday or Monday) in order to allow Welling to be there. Doing this near the weekend eases the burden on the SV production, which needs Welling on set every day if possible.
If it doesn't happen this weekend, then it might not be until NEXT weekend before we hear anything official.
This is all speculation on my part though. Maybe Warners will just issue a memo?
...nah.