From what I can see ToT closed in early January and Guardians opened in late May, with the opening date announcement coming in mid-February. I think it's the closest comparison we can make since it was a re-theme of an existing ride which required some new tech but no major construction. I'm not sure how involved it will be installing those new tunnels though, so it might take a bit longer. I think mid-May is unlikely. Even if they finish by then they would probably use that time for touch ups and press previews, and then formally open Memorial Day weekend. That June date actually seems realistic, but I doubt it's a firm date - maybe it's an internal working date, subject to change if they run into complications when they start work.
Based on how Guardians played out, I'm hoping for an announcement next month.