It looks like one lift would be ~600 vertical feet and the other ~900 vertical feet. Pretty short by Utah standards.
I don't know where the break-even point for the Summit development is, but I think it's got better prospects than most Utah ski developments. As I see it, there are two huge challenges in the Wasatch: 1) ridiculous oversupply of private land (Park City/Deer Valley, PowMow, Snowbasin, and Wasatch Peaks Ranch, plus tons of other mountain real estate that's not attached to a big ski area), and 2) essentially zero participation and little apparent interest in the market from anyone born after 1970. I think vacation homebuying among baby boomers has already peaked, and the coming years will see more and more people exiting the market without replacements entering the market, which means a constant availability of below-cost-priced secondhand homes. And if the market shows any signs of heating up, there are tens of thousands of potential homesites that will start flooding the market, keeping prices down.
To me, this indicates that the only chances for a profitable ski real estate development are 1) if you figure out how to artificially generate scarcity; 2) if you can differentiate yourself in the market in a way that actually motivates Gen-Xers and Millennials to buy; and 3) if your real business benefits enough from additional residents to offset low-margin or money-losing real estate deals (example--Deer Valley can count on each incremental real estate sale for a reliable stream of high-priced season passes, lift tickets, meals, etc., so they can sell that real estate relatively cheaply and still make a long-term profit).
Summit seems to have the best plan out there to tackle the first two strategies... advertising ahead of time how limited the real estate sales will be and separating the new village from the old PowMow development creates scarcity in that there's perceived value in being there, as opposed to a cheaper substitution good (like a condo in Eden or a home at the old PowMow development). And they've been working to build hype and interest among a set of rich young buyers that other areas would love to tap, but haven't been able to. If they can leverage these strategies successfully, maybe they can bootstrap themselves up to the point where the ski operation consistently pays for itself.