Gamestop leaks seem to be all the rage these days, and this time Borderlands GOTY edition appears to be on the list. Naturally we'll have to wait for an official confirmation to see what it contains, but it's not unreasonable to imagine it'll follow other GOTY models.
If the GOTY edition is real, then it's safe to expect Borderlands to come preloaded (or perhaps with an additional content disc) with DLC. This means that anyone unfortunate enough to have not played Borderlands yet may want to hold out to ensure they get the maximum experience.
Current DLC for Borderlands includes The Zombie Island of Dr. Ned, Mad Moxxi's Underdome Riot and The Secret Armory of General Knoxx. Quite a lot of bonus game time for an already excellent game, so it may just be worth the wait!