I agree with a previous poster and will probably go around 2020. I mean, HKDL wasn't exactly amazing when it first opened up either. There were not enough rides and TOO MANY PEOPLE.
I know for sure it will be full and crowded every day for at least a few years after opening.
I'm very interested to see what it will be like with the China-copy park right next to SDL. It's said to be even bigger than Disney.
I'm super excited to see all the new stuff they'll be doing!