It looked like a considerable amount of time had occurred from the moment on the church steps of the baptism and everyone was headed to Vegas right after the baptism to the time the movers were at the Corleone home moving things out for the move out West. It seems like that transition would have been a week or so. And Connie shows up on moving day ranting about Micheal having Carlo killed?
Wouldn’t Carlo and Connie have talked that night of the baptism by phone? Her in Vegas and Carlo still at the family house? Her asking him when he could come out to Las Vegas? Timing doesn’t feel right.

Sure. Connie heard Michael tell Carlo he couldn't go to Vegas--"it'll only be a couple of days." But Carlo went missing immediately. She'd have suspected Michael--and murder--immediately.
But, having her barge in on Michael and Connie during the moving made for a much more vivid scene. As always: Drama trumps logic.

We debated in How did Connie know Michael killed Carlo thread:
Connie's “Read the papers -- read the papers!” and return from Vegas and confrontation with Michael, happened within a couple of days after the hits including Carlo's all on the same day as the Baptism

No doubt As always: Drama trumps logic and sells tickets