Probably into the 50-55 bracket, since there's not enough people for a 50-54 bracket and then a 55 only tier. Which sucks either way you slice it.
that is a terrible way to do that.
you cannot group players that a) dont have all their abilities and b) all their talent points spent. that is innately unbalanced and will destroy any semblance of competitive PvP in this game.
however, the new bolster as RobHinkle outlined would allow a 10-34 and 35-54 bracket as was speculated based on datamined info. which leaves level 55 players in the same spot that 50s are at now