No, there hasn't been anything given to us yet that tells us exactly what happened in that missing time. As you said they are only giving us details as they are relevant to the story line.
This is what Noah Wyle says about it:
"We employ a bit of a time jump," Wyle explained. "The first episode starts seven months after the finale, so a lot has happened in the interim. This new race of beings called the Volm have landed, proven themselves to be trustworthy, and pitched an alliance with the humans to fight their common enemy, the Espheni, the Overloads of Skitters, we met last year."
Lots of shows do this sort of thing to encourage the intrigue and get people wanting to find out more. As Ross said JJ Abrams seems to be fond of doing this, having used it as a major plot point in shows like Fringe (where we jump 20+ years into the future and we watch as they rediscover and explain what happened) and Alias (where Sydney wakes up with no memory of the previous two years and we watch as she rediscovers what happened).
Falling Skies is a little different in the sense that they all remember what happened and we are the only ones that don't know. In addition to the bits and pieces of info they give us throughout the season they have still left it open to dedicate entire episodes to this missing time.