My warrior has been my main since 2005. I've been taking a break from WoW and haven't played for the better part of the last year, but the warrior will be my main again when I come back for WoD.
I've never been too big on alts. The only "serious" alts I've had have been my Warlock and Paladin, but you can easily see a huge gear discrepancy between those two and my warrior. You could tell the warrior is my main just by inspecting and comparing the gear.