I think it's close, but San Diego should be enough to tip it blue. Here's how the counties voted in 2012.

https://en.wikipedia.org/wiki/United_States_Senate_election_...

Edit: I was curious so I ran the math. It's super close, but republicans barely win. In 2012, Republicans scored 1,786,934 votes in green counties. Democrats scored 1,774,135 votes. That places republicans winning by 12,799 votes or with 50.18% of the vote.

That makes the new "Southern California" a swing state.

Temporarily at best. They have been active targets for Dem takeover for decades and absent massive population shifts the demographics will fairly shortly ensure that occurs.