I'm guessin that release is not far off since they are having a live game showing (<-link) Wednesday night , and they are releasing the game to critics and those who put out trailers. Looks like a good expansion.
Trailer here

Woah! Now heres a deal.   https://www.humblebundle.com/weekly    you can get RO1 RO2 and Kiling floor for about 3 bucks TOTAL!

Also has been confirmed that this applies to Rising Storm. If you already own RO2 when Rising Storm comes out, you get RS at a discounted rate.