I would be very very very surprised if RO sells 50k copies. I mean, I would also be happy for devs, because I support independent gaming companies *by design* but I don't think 50k is realistic.
By some of my calculations around 70-80k people, max, play COD2 online. COD2 being BY FAR the most popular WW2 shooter, NO MATTER what you may think about it (Personally I think it is very good but as I say it does not matter if it's good or bad - it is popularity that matters for purposes of this post.) Just start All Seeing Eye and do some math.
Now, assuming my math is generally correct, and each and every COD2 online player buys RO that's 70-80k copies sold. Fine, but it will never happen. Considering RO is much more demanding, more realistic (= less popular, I am afraid) and it does not have a single player component (it is safe to assume SP component was motive to buy even for those that now play online), I don't think it can reach 20, perhaps 30k copies max.
I sincerely hope this numbers would be OK for devs as well, and I do hope they manage to out-do this estimate, but I am usually always right because I am so smart (LOL this last part is a joke)
Oleg