I'm not a big fan of many of the TPC courses, the one in Scottsdale to me is a pretty poor course, although the scenery is great. The TPC at Sawgrass is the most famous of course and would be a decent add to WGT.
The British and US Open courses will find their way to the game, so Turnberry, Pebble Beach, Pinehurst, Royal Troon, Carnoustie, Shinnecock Hills, etc. will eventually be on here.
I would like to see WGT add another course each year outside of the 2 Open courses. Some of the great US courses are private, Winged Foot, Southern Hills, Augusta National but if they host the US Open I assume they will be fair game for WGT.
Courses like Harbour Town, the TPC at Sawgrass, Torrey Pines, etc. that are fixtures on the PGA tour would be nice to see come up every year.