There’s been a lot of discussion about possible new weapons in the forum, and it hasn’t even been that long since the latest ones. If you want to find out about other’s ideas, I recommend searching the forums, but here are a few links:
Adding new weapons is something the devs have expressed their desire to do, and I think (at least practically) promised that they will come. What those weapons will be and when they come out, we don’t know, and adding them is a bit more work than just designing their appearance and moveset. In particular, each new weapon really should have a purpose, a fundamental difference to the existing ones to give a reason beyond mere visuals to choose that weapon over others. As an example, the Hochland Long Rifle has been suggested several times already, but I don’t think it would differ significantly from the current Handgun. Accurate, long range, high damage, long reload are words that describe them both (and that define the weapons’ place pretty well, I think).
There really aren’t that many options that work well within both the game and setting, and aren’t mostly visual alterations to the current options.
As an aside, I also don’t think they will be tied to DLCs, or even released as a separate one. As far as I know, the devs (and the players) weren’t that happy with how they worked in VT1, so I suspect they will be released as separate content update, equally available to everyone.