It will be broadcast only if MLG picks it up as a title for their 2008 season. They haven't announced any games for that other than Halo 3, so nobody can be sure yet. However, if they do have it at their events, it would be VERY likely they would have a live stream specifically for smash during the course of the events(free if you have an account there). As for whether or not it would make it on the tv show, nobody can be sure until it happens.
As a side note, technically more people play Halo 3 then Smash (especially in the competitive sense). MLG's user count was somewhere beyond 250,000 before they acquired gamebattles and merged their user database, but smashboards current total only sits at 89,303. Even because of the slight difference in user #, you should be almost certain they will pick Brawl up for their '08 season. If it wasn't enough of a sign that they have a gamebattles ladder for it already, the fact their last few SSBM tournies had a large (and increasing) number of players entering shows that there is a desire for players to attend MLG events specifically for smash.