Not necessarily. If Trump and other republicans start to campaign in CA and expose the problems caused by democrats they can turn a few votes.
I seriously doubt they could win the state in a presidential election, but if they can turn losing by 4.3 million votes as they did in 2016 into only losing by 2 million votes, this ridiculous talk of a national popular vote will go away rather quickly.
Everyone knows the problem CA is having without having Trump go there and waste his time and money.