TerraCoin doesn't really change anything in the bitcoin chain except for the block rate and diff retarget rate. I don't think it serves any useful purpose except as a pump n' dump scheme.
It doesn't matter if it gets 51%'d now or not, it'll be dead in a month due to merged mining anyway.
It's a pointless fork.
It's actually worse than pointless, since the addresses used start with a 1 the same as bitcoin. This is something that the creators of the other alternate chains did not mess up! A terracoin address is not easily identifiable as a terracoin address.