Due to TSW2 routes not having all the new features that TSW3 offers, I think a price reduction for all old routes would be suitable, as the routes are not at the highest standard that we can now expect from dovetail. A reduction on all platforms would be appreciated, and would make me feel much better about investing in a route which I know is not up to the current standards.
Buying TSW2 content will give you TSW3 versions so I can't see that happening. Those routes will still benefit from some of the TSW3 features. They didn't change this going from TSW2020 to TSW2, so it's unlikely.
I feel like a price decrease would be more appropriate for the TSW 2020 routes. Those are definitely the most outdated, and one should never have to buy Rapid Transit for $30. Some of these routes have things like outdated skies (worse than the regular TSW 2 skies), scenarios lacking the option for immersion controls, some are incredibly short in length, outdated physics, etc. Of course, I don't think it really matters. These routes go on sale constantly. Rhein-Ruhr Osten is always down to $8. That's about three cans of soup. It's cheaper than what any sort of price drop can offer. If the TSW 2020 routes are constantly on sale, expect TSW 2 routes to follow. You can always find LGV Mediterrenne for the price of a cheap pair of t-shirts.
TSW2 may well be cheaper than newer DLC coming out in the future. It may be that new DLC has a higher price and the older ones stay the same. That’ll be the difference in price you want for older and newer content sorted. Nothing has been taken away from the old content so I can’t see them reducing the standard price as well as the fact that most people can get them at a discounted price anyway in sales, except xbox players of course, who only get a sale when there are three full moons in a calendar month.