JavaScript! Its very universal once you learn it you can write basically anything (other then games). It's also very simple compared to other languages.
Here's how the math works out:
4k: 3840 * 2160 = 8 294 400 pixels.
8k: 7680×4320 = 33 177 600
8 294 400 / 33 177 600 = 0.25
8k has four times the pixels of 4k. So if we assume perfect scaling then 4k 60fps = 8k 15fps.