I am sorry, yes, WE means weekend. I am French living in Germany and this is part of the "continental" way of writing. Even in Denmark where I stayed a couple of years it was used all the time.
I think weekend? Esoteric contraction but I guess if OP is a German native then it saves more typing when compared with Wochenende.
As another German native this is it, yes. I am not sure I saw it before in English, but it is a fairly common abbreviation, at least in chats (although I think my iPhone automatically replaces WE with Wochenende even though I never set it up to do so).