You can have a look at the proposed new forum software here: https://meta.discourse.org
Some big sites that are using it are mentioned here: http://www.discourse.org/faq/customers/
Nothing major will change for users that access the forum exclusively from a PC (other than the change in layout and some more advanced functionality, but the basics remain the same)
Have a look at the user statistic for last week. We didn't have any major festival news or any advertisement or promoting on Facebook. Returning v.s. new visitors was 78% v.s. 22%
As you can see 80% of the visitors is 25+ of age. Only 20% is in the 18 to 25 age group. The average age of a Roskilde festival visitor is ~24.
This forum community will die without new, younger users. In fact, it was already dying the last few years as part of the official Roskilde website
We are only seeing a small increase in posts this year thanks to advertising and promoting on Facebook.
If you are concerned about the quality of posts from casual visitors, there are some features in Discourse that will discourage or even block one-liners ("Daft Punk!", "RATM!!!11111one" ect.) and promote more mature discourse
All that being said, we are very interested in the opinion of our current regulars, so please feel free to raise any points of concern or other questions