What if a couple people worked day in and day out on a big expansion?
There are plenty doing so, but if it took Bethesda, (At the time like 70 people) like 6 months to make the Shivering Isles, how long do you think it will take 5 people to make a massive expansion?
Now, I'm making a fairly small expansion (Adds my own island about 1/5 the size of Skyrim) and I'm working alone, but I plan on finishing in like July or August hopefully. Here's my progress so far, just a heightmap and some basic LOD: http://cloud.steampowered.com/ugc/488876271486080127/9DCBF207E2D73F2A7C84A046E91C2913C81AC59A/