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This looks like it could be the next big route push for Superchargers. Take look at the Google Maps route that I overlaid with a screen capture of Tesla's 2015 map:
The route looks like:
The Dalles, OR - Open
Pendleton, OR
Baker City, OR
Boise, ID
Twin Falls, ID
Tremonton, UT
Salt Lake City, UT - Open
There are already strong rumors of Pendleton and Tremonton. That just leaves Baker City, Boise, and Twin Falls in between. Remember these locations could also be a nearby town.
This map also implies Richland, WA being added in 2015 to connect the Portland, OR area to the I-90 route, and a Supercharger in Bend, OR.