Dan DiDio has said a few things about the new Adventure Comics series in the last couple of weeks over at Newsarama.
From the 12/24 edition of "20 Answers, 1 Question":
Oh – and one last thing that I wanted to mention before we go – the content for Adventure Comics #1 has changed – I think it might be out there that Mon-el is in issue #1. The reality is, that the storyline that we were going to put in as the launch of Adventure Comics has actually moved into Superman comics. While the Legionaries will be appearing in Adventure, it won’t be until the second arc of the series.
And from this week's edition:
9. As a person asked – the solicitation for Legion of 3 Worlds #5 confirm that the Legion will be spinning off into Adventure Comics. What can you say about the Legion of Super-Heroes in Adventure Comics?
DD: What I can say right now is that Legionnaires will be featured in Adventure Comics and in Superman. Those storylines, featuring those characters tie into their other appearances that we saw in the Superman mix earlier. It’s all made clear in Adventure Comics #0.
So Adventure will be an anthology with rotating leads? How many times has DC tried that and failed?