I'm not sure, but only because I don't know what turn-based tactics tournaments there are now. If there aren't any, I doubt SH:T is going to be the game to play competitively.
Depending on how this improves the previous turn-based Space Hulk video games, people may just play those two at their local gaming conventions. There'd also have to be a huge marketing campaign to push this as the #1 turn-based tactics game, or #1 Warhammer game right now. It's also got to compete with the other two TBT games coming out, Mechanicus and The Horus Heresy: Betrayal at Calth.
based on my knowledge and what I have seen it seems as though Mechanicus would be the competition to beat if anything and what i got from their fb page they hinted at march 21st. but all in all i think it will boil down to who do you want to play as and if the game is done well. my knowledge of tactics comes mostly from fire emblem and final fantasy tactics that came our for the game boy advance SP. I'm still crossing fingers for an alpha invite.