Titel said it all.
Maybe a double xp weekend to celebrate Kilgore and the near-future ultimates? 
Would that be in addition to the permanent double XP the ultra combo breaker packages already have in play?
yes. all double xp triples then.
1500 xp get 3000 xp in double + double xp (weekend) = 4500 xp (triple.)
2000 xp becomes 4000 xp and in triple 6000 xp.
Probably not going to happen, they’re doing weekly evens now every Tuesday. Those include sales, XP events, character releases, skin packs, etc. They’re going to keep them for stuff like that, your best bet is next week if they decide to do one.