Missed this one when it origianlly was announced in Wizard #187 (still sitting unread in my mile-high stack of books). Geoff Johns and Brad Meltzer say the Legion will play a major role in their upcoming JLA/JSA cross-over event "The Lightning Saga". From the interview:

Beginning in April's Justice League of America #8 and spiraling into Justice Society of America #5, Meltzer and Johns, along with artists Shane Davis, Ed Benes, Dale Eaglesham and Fernando Pasarin, make history with a five-part crossover entitled "The Lightning Saga." The epic tale aims to tie together the legacies of the JLA, JSA and the far-flung 31st Century Legion of Super-Heroes, and not only does it collect a massive array of superheroes for an epic adventure, Meltzer and Johns' tale makes history as the first-ever, in-continuity crossover between the JLA and JSA in their respective books.

Going for broke right out of the gate, the writing duo not only pair big guns like Superman and Batman alongside staples like Jay Garrick and Wildcat, but tie in the often-detached 31st-Century superteam, the Legion of Super-Heroes, into the grand tapestry of DCU's caped legacy.

"The Legion is as important to the DC Universe as the Justice League and the Justice Society," Johns explains. "That's what we're trying to illustrate. There's stuff that's going to come out of [the crossover] that's going to propel the Legion and show them as having a very important role in the DC Universe, even if they're not here."

Meltzer adds: "The Legion, when they were established, they were inspired by something that happened in our time. So to me, that tie is a thread that [has] sometimes been frayed and lost, and it's one that I think should be vital and we're really trying to show it."

"The Lightning Saga" can be found on the Legion AR Checklist for 2007.