Developer Fatshark have revealed that they will be adding Mod Support, Dedicated Servers and the first DLC for Warhammer: Vermintide 2 in April - just next month.
Fatshark have laid all this out in their development map for the next couple of months for Vermintide 2, which is available on their site.
You can check out the roadmap here. Here is it in general:
Fatshark are aiming to get Dedicated Servers working in April along with improved matchmaking and stability. They're also "putting the finishing touches" on Mod Support and hopefully it'll be ready for April too - but notice how both of these are in blue and extend into May, so this could slip.
In green though, so will probably not slip, is the first DLC for the game in the form of 1-2 maps. These presumably will be paid for, although the roadmap doesn't say either way. Fatshark say that they "plan to release regular DLCs".
It's certainly be a good week for Fatshark, as they revealed that in just a few days of release Vermintide 2 has sold over 500,000 units - and that's on PC alone since it's not available for consoles yet. Fatshark CEO Martin Wahlund said of this, "We are proud and happy that gamers worldwide have taken Warhammer: Vermintide 2 to their hearts. 500,000 games sold was a milestone that we had, but not less than a week after release." Excellent news.