It was a sleep cue for DD too but she kept escaping her wraps (even the proper swaddles!!) so we just bit the bullet and put her in a sleeping bag. She was already sleeping through and it continued, she didn't miss a beat She was only 10 weeks old.

I think kids surprise us sometimes and cope a lot better with change than how we expect them to. I've worried about sleep cues and habits with DD but have found she often copes well with change and the worst case scenario is things can be a bit erratic for a few days or nights until we get over the hurdle.