There would have to be enough vehicles willing & capable to travel that route before Tesla would invest in expanding to connect the lower 48 to AK.
Bragging rights?
Past supercharger build patterns might suggest a 3rd criterion: that sites only get built after other higher priority sites get built (or, alternatively, they get built in large multi-site deals with chain hosts). In recent years, I'd guess that 95%+ of supercharger stalls are built to expand capacity (relieve overcrowding), rather than to expand coverage (see, for example, California). I understand that Tesla has been working to increase supercharger hardware production, as well as human capacity for permitting, etc. But with Tesla selling cars like hotcakes and poised to open superchargers to non-Tesla EVs, more effort than ever will be required to mitigate overcrowding.
For better or worse, the most immediate issue for Tesla with increasing production (Cybertruck or no Cybertruck), will continue to be expanding overall capacity, rather than expanding geographic coverage. Let's hope they get out ahead of this, but I'm not holding my breath. More likely, gaps will be filled in with 3rd party, slower, CCS chargers before they get superchargers.
I can't wait for that trip up the AK highway superchargers in 2028!