I'm sure even if they don't make a DLC for it then someone could in theory make one. No one can answer the second one lol. Jk. And yes a few I wouldn't want to ruin it for anyone though.
I honestly don't know. All I was told was it wasn't Fallout 4 and it's unlikely to be Elder Scrolls VI. So it would mean a new series. Perhaps a game to speak to wider range of people? Or a MMORPG?