Tesla also shows that they plan Superchargers for Adin, Newell, and Greenville (of all places.) (These spots boggle my mind, but that is another thread.)
Anyway, Tesla sometimes puts in Superchargers along highways in clusters. Probably saves some money on construction costs. Susanville may be one of those locations that will be built when Tesla has lined up one or more of those other putative sites.
And, don't forget the Red Lion Hotel as a potential spot. It already has two destination chargers. I understand that the owner of the Red Lion (and the Hotel Niles in Alturas) drives a Tesla. He might be the go-to person to get Superchargers installed on his property. That spot is sorta close to the junction of US395 and SR36, and it is likely that more travelers would be driving on SR139 or SR36/44 that heading north to Alturas until Tesla builds out 395 to Lakeview and beyond.