[Updated/corrected 5/7/2022]
Here's what we know about Leakgate: Justice Alito's draft "Opinion of the Court" in the Dobbs case, as published by Politico, is genuine. It was the first draft to be circulated; it is labelled "1st Draft," and it is the Court's custom to circulate drafts of majority opinions before other drafts - dissents, concurrences - are circulated. The Alito draft was dated February 10, 2022 (and, one may assume, it was distributed to the other Justices on that day), which is about two months after the Court heard oral argument in the case. If it were adopted by a majority of the Court and issued in this form, it would overrule Roe and Casey.
From those facts, we now know, inferentially, some things that we didn't know before the leak. First, that the Court has decided the case in Mississippi's favor. We know that because that's how "opinions of the Court" get assigned to individual Justices: the Justices vote on the preferred outcome in the case (Mississippi wins/Dobbs wins), and the senior Justice voting with the majority then assigns the task of writing the "opinion of the Court" in support of that judgment to one of the Justices in the majority (including, possibly him/herself). So the draft opinion's preferred outcome - Mississippi wins - must be the preferred outcome of the Court majority.
