I saw on the stream that TSW3 will allow us to load preserved content but it said "Preserved collection content won't run new weather, lighting or gameplay features." Can we expect any updates to TSW2 DLC so it can have these features too?
They will not be available at launch for the preservation routes, however I do believe they will receive them as part of preservation updates.
Stated by DTG Alex on Discord: Preserved Routes that are on TSW3 will get the dynamic weather (lightning, thunder, rain splashing effects). The volumetric skies and new updated lighting is only on the TSW3 Launch routes (SEHS, Cajon Pass and Kassel) and also on Spirit of Steam.