I suppose we should define what a "tipping point" is. OP did not do so explicitly.
I would say "tipping point" could be defined either from a demand (desire) standpoint, or from a practical usability standpoint.
As far as practicality is concerned, could a large portion of the population be as well or better served with an EV than with a gas car, if their next purchase (wouldn't happen overnight for everyone) were an EV instead? Probably.
-More households than not have more than one car, so an EV need not serve 100% of the needs for everyone for every trip, much like not every car need be a pickup truck capable of towing a 30' camper.
-Do EVs and PEHVs have lower cost of ownership than a similar gas car, accounting for depreciation? Probably. The Leaf depreciated quickly, but the Volt and C-Max seem to be holding value very well. I'm guessing the Model 3 and Bolt will hold their value very well too, and cost less over time than an equivalent gas car, unless we have a major battery breakthrough.
-It's probably accurate to say that very roughly half of all people could get by on the electric range of most PEHVs for most of their daily needs, nevermind the range of a full EV.
-It's probably accurate to say that half of all people could reasonably charge an EV at home on 110v to cover those range needs. The need for 220v chargers wouldn't be universal.
-It's probably accurate to say that the grid in most places could handle the influx of half of all people buying PEHVs and EVs charging at 110v at night, at the rate that people normally replace their cars. Half of all cars will not magically become EVs overnight.
As far as demand/desire, I don't think people are aware of them enough yet. Electric vehicles only seem to be in the consciousness of a minority, and even fewer are actually buying them. We might see the demand "tipping point" in only a few years though, depending on how well they're advertised.
EDIT: As a side note, although I drive a 75mpg+ hybrid, I've largely replaced my car for around-town trips with a couple of electric bicycles. I managed to put together a nice 1000w geared hub kit with ~30 miles of range for under $250, and it's a hoot to ride.