There actually is a measure on the ballot to modify prop 13 this year: https://ballotpedia.org/California_Tax_on_Commercial_and_Ind... — as you said, this is the year for it to pass.
It'll be much more expensive to hold commercial real estate without it yielding income, so it should reduce the commercial vacancy rate.
This can (a) raise a whole lot of revenue, relieving local/state budgets so they can hopefully stop needing as many stupid short-term workarounds which have proliferated the past few decades, and (b) allow future commercial property taxes for newly purchased commercial properties to be lower than they otherwise would be, encouraging more turnover, especially for underused properties.
The obvious follow-up would be to also change the law for residential properties owned by large-scale landowners (say, companies which own large apartment complexes or dozens of homes).