So is this a successor to the DE-10 Nano (the board the MiSTERFPGA project is based on)?
(after looking at corescore probably not, as it'd be way too expensive. that being said, the DE-10 Nano is getting old, are there any potential successors coming)?
There are many already available, e.g. ZedBoard, someone just has to do the work to target these other boards and their peripherals/layout.
Nothing is really comparable to the DE-10 Nano's combination of capacity, embedded ARM cores, memory, HDMI scaler, and (most importantly) price. The ZedBoard fails the last test: it is a fair bit more expensive than the Nano.
I am keen on the MiSTex project though. The plan is to come up with something that is more flexible than MiSTer to support different targets. So for example, you might be able to target a simpler core to a simpler device and vice versa.