I see some possibilities: announcement at Jump Festa, end of the demo (it could be the 'surprise', although I'm expecting something like a summon/city/whatever) or E3 (or even TGS if prior to it they've only announced a release window).
Regarding the English version, yeah, I can see a trailer being released soon (even in Jump Festa. They could play it there in Japanese and then upload it in English too).
And well, I'm glad to hear this about the lenght, although it's the standard in the series. Now Tabata, just give the possibility of controlling Cor and I will forget this week