I fail to see the downside of a CA General being a firey, high-energy showdown between Feinstein and de Leon. It'll drag dems to tje polls and might make Republicans stay home, which is great for House candidates.
If the general election is Feinstein vs de Leon, that would be amazing. However, to really get the benefit of depressed Republican turnout, the Governor's race needs to be DvD as well, or maybe at least Democrat vs Ultimate "Some Dude," although I'm not sure how bad that would be for the CAGOP in terms of turnout.
While not as interesting, I'd also note that Republican state legislative candidates in California would be in trouble if no Republican made it to the GE in CA's Senate/Governors races. They rely on ticket splitting and optimal Republican turnout to stay afloat in Romney/Clinton or Obama/Clinton districts. If they see lower turnout and more straight ticket voting in 2018, Democrats could really sweep legislative races and build a comfortable supermajority.