This is basically what the structure of the trailer was, so I'd say that's pretty much it on the head. We know as well that they'll be establishing the different time periods thing in the 3DS game too, so it makes sense.
I just hope we get some decent game time in the present. The reveal in LOS1 was so good. But then I'm not sure if anyone remembers this, but didn't Mercury Steam troll the series a little a few months ago, stating they were done with it past this game, didn't want to only be known for it, etc? Something like that any way. I found it kind of surprising, given they haven't really did much of note before, and I kind of just assumed this would be a middle installment before a final 3rd set fully in the present day. So yea, hopefully it fulfils its promise.