Maybe I'm wrong, but I think that they just messed up the continuity. I think the altercation is supposed to occur within a few days of the hits. The hits on the dons make the newspapers, then Carlo doesn't show up in Vegas and before too long Connie figures things out (she's a Corleone, too) and flies back home. The moving van and packing up the house seems out of sync, and in the novel that actually does occur later.