If you had any clue what security was like there and you understood we probably wouldn't get to see this footage at all otherwise...
I would like to see the bad guy just win for once. I don't like Thanos, but they can't keep losing can they. Make the people walk out of the theater and say WTF! happened, just once. Then of course Flash can come in and kill him in the sequel because that's how it should end.
My goodness, I've been waiting for this movie my entire life and I'm still not ready for this. Black Panther and Winter Soldier defending Wakanda... Please just let me live long enough to see these next 2 Avengers movies. I can then rest happily.
If you had asked me before the leaks I would have said probably around the time that Thor comes out (November), but since there's crappy leaked versions everywhere now I'd say it's likely only a matter of time.
Sometimes they release it within 24hrs of the bootleg because the bootlegs look so bad. But if they haven't put their CGI polish on this yet you might not see it until football season.
I wouldn't be surprised at all if Thanos appears to have completely or nearly completely won at the end of the first movie.