You laugh, but hear me out.
In the wake of LCD and Strokes shows there the first week of April I jokingly said to friend "Anyone can fill that place, including Metric". Other "smaller" acts that have played there have included Flaming Lips, My Morning Jacket, Phoenix, Arcade Fire(2 nights in August 2010) amongst others.
Metric filled Molson Amphitheater in Toronto(anyone have a final audience figure?), played arenas in Victoria/Kitchener and have been billed very high at 5-6 Canadian VFests, Voodoo Fest in New Orleans and APW Festival in NYC. I saw a good 8-10,000 focused around their stage for their Chicago Lollapalooza appearance last August, plus the signing lineup was equally as long as the last time they did one in Vancouver. They were on a double bill with Phoenix that sold out 6,000 in Los Angeles.
We all know Metric have surprisingly strong fanbases in Toronto/Montreal/Vancouver/Alberta. NYC/LA are competing with those Canadian markets and their Pacific Northwest shows have been packed for a good 5 years now along with other places near the border. I'm not even sure they'll ever be big enough to do a Canadian arena tour, but trying one arena in the US would be a career high point for sure.
That said, they'd need to have all their "ducks" in a row to make it work. No regional shows for a bit then advertise heavily including Toronto-Atlantic Canada. Have guests and bonus songs like the Toronto Amphitheater show, good opening act(s).
Don't worry, they'll still play clubs from here on out. I saw them do full band Fantasies material in a 300 capacity club.