[...] I'm self teaching myself [...]
In the video you posted the guy doesn't actually play the whole piece so it's difficult to say. Also I'm not experienced in playing the keyboard as I play the piano. Keyboards and pianos differ in the weight of the keys, sitting position, dynamic contrast, tone and number of keys among other things. Anyway from what I understand it's just a bunch of chords and arpeggios if you get a teacher you can learn to play stuff like this pretty fast. I think I could play something like this, with ease ,3 years into my piano study so I'd use that as a rough estimate to the maximum amount of time it would take for the average person, minimum probably several months. These are all very rough estimates, best to get a teacher and ask them the same question.