The "problem" with adding a resort stop on the Epcot loop is that you've now made this a significantly longer trip time wise. Some will hate that, some won't care.
Some people will care, but that's probably okay with Disney. At worst, some people would decide to take the bus instead of the monorail. We know that the monorail is far more expensive to build than a fleet of buses; I don't know about operating costs, but if buses are cheaper, then moving people from the monorail to buses is a win for Disney.
One resort would mean one 60-90 second stop. While some might gripe a little, I don't see that being a major issue in the long run.
That said, Disney seems to be intently focused on DVC as its development right now, and most of those seem to be built around current resorts (I would presume that there's a significant cost-savings in development when the infrastructure and resort services are already there). An independent resort in a currently vacant area does not seem to be the approach they are taking.
The problem with this is that Disney's out of current Deluxe resorts. Once the Poly gets built, the only Deluxe property without a DVC add-on will be the Yacht Club, which has its own set of problems (there's little to no land at YC, and there's already a DVC at Beach Club).
I get the impression that OKW and SSR sold out because they were built before the current Deluxe add-ons - I doubt they would sell well today when compared to all the existing DVC properties. The most credible rumors today point towards a DVC resort within walking distance of DHS, especially if DHS gets Star Wars. But people love their monorails, and I think that would be incentive enough to sell an Epcot DVC very quickly.
Secondly, I don't think Disney would need to add a second Epcot line for a resort loop. That was necessary at MK when the TTC actually served as a transportation hub for MK guests. Now, with direct bus access to MK, very few people "need" to take the monorail anywhere. The only people who would be truly inconvenienced by a (slightly) slower Epcot monorail are A) resort guests at the Poly, GF, and CR, and B) park hoppers. I can't really see the first group objecting strongly, since they're on a resort loop themselves. And I'll bet Disney would be willing to make everybody wait the extra 3-4 minutes (or whatever) if they can make millions on a new Epcot DVC resort.
I'm not sure how "buildable" most of the land along the Epcot route is, but looking at Google Earth it appears that there are at least three big resort-sized spaces along the monorail route.