Sanders strategy is the same today as it was yesterday. His supporters don't seem to get that.
The reality is that if Sanders voters don't show up today it's entirely on them. Bernie's strategy today is exactly the same as it was yesterday before the announcement. That strategy has two parts:
1. Protest the media's proclamation of Clinton as the presumptive nominee based on pledged delegates and SD commitments. Sanders expected that proclamation to come tonight as soon as NJ was called for Clinton (he has acknowledged she's going to win there). Instead, it came a day early. So he made his protest a day early.
2. Fight to get the biggest wins possible in CA, NM, SD, ND and Montana -- especially in CA -- in order to cut into Clinton's pledged delegate margin (which likely will be over 300 delegates after NJ is called) and use those results and GE polls to try to convince SDs to switch before the convention. Nothing about yesterday's announcement changes that strategy one iota.
Oddly, its the Sanders' supporters that are saying California is now meaningless, even though California is exactly as important as it would have been without last night's announcement. It would seem that they believe that a lot of their fellow Sanders supporters aren't revolutionaries prepared to follow their leader who refuses to quit, but instead are low information voters or fairweather supporters.