There's about 350 new SparkEV inventory according to autotrader while about 250 were sold in Feb. Assuming sales hold up and no new available, that's about 1.5 months inventory. Back in Apr. 2015, about 950 were sold, about 250 in May/June before inventory got tight. That suggest about 150 new a month coming into market. There's time to get it, probably until later part of the year if sales/inventory stay the course.
But if you want the best deal and sales hold up, I think sooner the better. I see some new 2016 in OR selling for $22K. If that's pre-subsidy price, that could be $12K in CA, or even $9K in some counties of CA! I mean, what new car, EV or not, can you buy for $12K or $9K, especially one that performs like SparkEV?