If I were to speculate--and this is pure speculation:
(1) Expansion of the current location from 10 to 16 or more. There is ample room adjacent to the current installation, either directly across from them or to the south.
(2) We are slated to have a Sales and Service Center soon (that is Musk-speak for whenever.) Perhaps Tesla will have Superchargers at this putative location.
(3) There is a lot of new construction just off freeway 41 near the Friant Road exit. Freeway 41 is the road that goes to Yosemite and Bass Lake. Since the existing Supercharger is off highway 99 and a 20-minute detour for those going to and from Yosemite from El Lay or the Central Coast, Tesla might decide to install Superchargers off this freeway.
(4) None of the above.