I have seen some posts on other threads about possible buyout bids coming after companies are released from their Confidentiality Agreements (CA). I too used to believe that the CAs prevented buyout bids, but according to IOC management, they do not. They simply prevent companies from taking such actions in the open market.
So the important thing to note, for good or bad, is that companies such as Shell, Total, etc., can make buyout bids now, or after the CAs expire, or after the selldown, or whenever. There are no restrictions on when they can make such buyout bids.
As to whether IOC has to release the news of the bid publicly, because it is a material event, is another matter. This depends on how the bid is worded. I would think that all companies involved would understand the legal intricacies here and would know whether their bid would likely require public disclosure by IOC or not, and would word their bid accordingly.
I hope this helps in evaluating the situation.