Hello, thanks for purchasing the sim! To answer your questions,
1. Yes, you'll need to buy v2 again as I'm considering it a "new sim" in that it has much broader scope and features, whereas v1 will be mainly limited to just British 1st generation DMUs. I'm still releasing several free updates to Diesel Railcar Simulator over this year and next year, and I'm sure they'll be worth your current investment. DRS owners will also get a discount from v2.
2. Steam release is indeed planned and keys will be distributed to those who bought the sim here!