My personal opinion is that any country represented needs to have 2 things:
1. Distinctive Architectural styles, &
2. Distinctive food options.
With that in mind the 4 pavilions that I would like to see next are:
1. Greece- this provides for wonderful architure, great ride possibility with a tie in (Hercules ascent to Mt. Olympus- a dark boat ride through the highlights of the movie), and a really good and popular food option for either counter service (Gyro stand with outdoor seating) or sit down.
2. Egypt- I envision a Sphynx pavilion that you would enter into and there are great ride options with this (a cruise down the nile or a thrill ride themed around archaeology-this would have to be different then the Mummy ride in Universal, but I'm sure they can come up with something), the food is not that different from Morrocco (to the average person please don't attack em to explain the differences), but the atmosphere could be excellent.
3. India- this could provide very different architecture and the food would be distinctive. For this I'm not sure what the ride options should be, but they pay Imagineers for that. Plus with Disney attempting to get into India to build a park this could be very easily accomplished for negotiating the contract, because they could have theri tourism office helping to book trips to Disney-New Delhi.
4. Russia- beautiful architecture and some interesting ride possibilities (Trans Siberian express anyone?)
I just wish they'd build something soon.