I think the more likely dynamic at work is soon-to-be-elected-governor of Cal....Gavin Newsom.
By summer of 2019, I expect Senator Feinstein to give intent to retire, and Newsom appoints himself into the job. He’ll appear in DC...give a number of speeches...get hyped by Time/Newsweak, and become this new ‘face’. By January 2020....he’s in Iowa and hyping some California agenda.
Governors have better success running than senators.