Upon downloading the Mechromancer pack and patch, I was having an issue where the game would load, and tell me my downloadable content was corrupted. I have since fixed this problem, but I found something interesting in the process. By the way, for anyone having this issue, I got it to work by making Steam verify the game cache, restarting Steam, and then starting BL2 again :) Anyway, on to the nitty-gritty.
Located in (for me) D:\Program Files (x86)\Steam\steamapps\common\Borderlands 2\DLC, there are folders for each of the "DLCs" so far. I preordered the game from Gamestop, so I am a Premier Club member, and I have TCSD. I have also got the Mechromancer pack, and thus I have these folders:
POGamestop contains data pertinent to TCSD, POPremierClub contains stuff for the promo unlocks like bonus skins and Golden Keys. Tulip apparently has the stuff for Gaige. While trying to figure out the problem I was having, I stumbled into Orchid\Compat\Config, which has WillowDlc.ini in it. To save space, I will suffice to say that this file seems to hint at Fast Travel to "Caves", "OasisTown", "Refinery", "SaltFlats", "ShipGraveyard", "Spire", and "WormBelly". It also looks like it talks about new heads for each of the current classes, and a new vehicle, referred to as "Hovercraft", with what looks to be three different variants, and a new raid boss. Aside from that one file, I also seem to have the content for it as well.
It is, as you suggest, preparation for what is likely the next DLC. This is how most of us found out about DLC 4 from BL1, as well. They included a good bit of hidden content in a patch released a few weeks before RR, just like this. 22:35, October 9, 2012 (UTC)
Acording to Randy Pitchford, the first two DLC are already in a very good shape, and the third one being already developed and is nearly a halfly complete while the forth is just sketches. He also mentioned that they will be adding more character classes if the Mechromancer is successful and they are planning to add free more guns in the game for us to find, on top of that he mentioned that they will try to implement nre cool features and in-game stuff but are not yet certain if they can make it happen but let´s keep our fingers across. The future of this game is surely looking bright and it is easy to see that this company more than anyone else, cares about their fans and are trying to make this game more awesome.—Preceding unsigned comment added by 220.127.116.11 (talk • contribs) 18:22, 9 October 2012