So that tweet was made by one of the Overwatch news outlets, but it was based on the Community Update 5 video from last month. Here’s another thread talking about it.
Per the video, they mention an “unvaulting”, but that could have just meant the fact that the skins that were available earlier in the year would come back to the OW2 shop, but that phrasing is what led to the information in the tweet, which was fully created by “Overwatch Cavalry”.
The big focus for OWL now is the 3 for 3 incentives they just announced a few days ago, which include the OWL grey skins, some player icons, name cards, and sprays. I don’t think they would want to add even more OWL stuff that could either confuse the community (“I watched for 30 hours, why didn’t I get the All Star skins?”) or get lost in the background of the other announcements, like the 3 for 3 incentives.
If the vault is re-opened, I’d imagine they do it with tomorrow’s big Halloween patch, and have the vault last 2 or 3 weeks. Otherwise, we’ll probably need to wait until next year to see if they re-open the vaults from last year.