I think you are correct in saying that it will end on a cliffhanger. Since they've already been approved for a season 3, I don't think they're going to end with everybody getting killed off. My guess is one maybe 2 of the characters will get killed off. They'll pull one of those build to the intense moment something major is going to happen and then the episode ends. We'll have to wait 2 years to see how it concludes. Haha, I hope it doesn't end that way!
They cut down to 8 episodes this year so they could move some of the story into season 3. RR Martin said he needs 3-4 seasons (10 episodes each) to tell the entire story. They shortened it to 8 this season, so my hope is they bring it back to 10 with season 3.
The other prequel series A Knight of the Seven Kingdoms is supposed to release next year. I don't think that series will have as much CGI like House of Dragons, so they could potentially get back GoT level and actually release a new season every year! hahaha, one can hope!