I would agree with the above posters that it's most certainly possible, but if you're planning doing anything outside of Disney (which I HIGHLY recommend), this trip would take at least 2 weeks. We just got back from 2 weeks in Japan and Hong Kong in April/May, and our itinerary was jam-packed, even only having 4 full days (and a few evenings) between the 3 Disney parks. I can see adding Shanghai and Beijing, making this a 3 week trip. My wife and I have actually talked about doing something like that in Spring 2017.
For me, I'd recommend 2 days for HKDL if it's during a busy time, otherwise 1 day would suffice for just the park. However we like to explore the hotels as well, so we did a full day and an evening (after exploring the city that day). For TDR, I found 1 day at Disneyland to suffice, as I frequently visit the other Disney Parks, and I personally found it to be a pretty standard Magic Kingdom park, with a few nice additions. Being that I work at the Magic Kingdom, one day was enough for me. However 2 days is highly recommended for TDS or one marathon slow-season mid-week day. We did the latter and completed everything, including doing our favorites multiple times. However we were fortunate to plan a week day the week prior to golden week and found very short lines for everything but TSM, which we did not do.
It's hard to say how much time shanghai will need until crowd levels are estimated in a more exact manor. I'm guessing a minimum of 2 days to truly experience a good portion of it, but time will tell soon enough.
For city/country timelines, I think Hong Kong requires at least 3 days for exploring the city, more if you want to see Macau, Ocean Park, etc. But for the city proper and some of the bigger sites (Victoria Peak, The Harbor, Kowloon, Ngong Ping, Po Lin Monestary, etc...) at least 3 days. Make sure to hit Tim ho Wan for great dim sum with a Michelin star, at dirt cheap prices. For Japan... that's tough. It's such a diverse country full of awesome things to visit. You could easily spend 2 weeks in Tokyo alone and not see all the "major" sites and cities. We did 2 days in Tokyo (not including TDR), a day in Nara, one in Kyoto and a few other small side trips. I felt like we barely scratched the surface!
Hope that helps a bit.