"we will see electric cars with ranges of 660 miles before 2030"
Driving 660 miles without topup is very much an edge case. If the battery is too heavy it badly affects your range anyway. I think car companies would eventually provide maybe 500 miles range at most for high-end cars once the technology can sustain it. That's about as much as a modern diesel can go on one tank. Most customers would anyway prefer a cheaper car with less range if they are never going to drive 500 miles at a go. 300 mile range is pretty good if you have fast charging.
Tesla model S 85D (85kWh) claims 'normal use' range of 270 miles. The electric motors themselves are very well understood and I doubt can increase efficiency noticeably, so theoretical 500 mile range EV needs a battery of about 160kWh. The limit of how heavy the battery can be without making the car impractical is about 500-600kg*, so you need specific energy of at least 266Wh/kg.
Current Lithium-ion batteries can generate about 160Wh/kg**, so it requires a considerably higher specific energy. Probably it will require a completely new battery technology to get to that energy density, so making it commercially available*** in 12 years is doubtful even for 500 mile range.
* for comparison, a full tank of petrol might way, say 50kg, and even a pretty big engine will be about 250kg. Additional weight for drivetrain and other ICE-related components not needed on EV approx 100kg more, 400kg total. Tesla's 85kWh battery is 540kg
**Tesla's battery would work out at about 160Wh/kg , the real value may be more as I guess the battery pack hasome structural elements adding weight. Per wikipedia, 100-234Wh/kg range, I'm guessing the higher ones are experimental
***I have no doubt it will be technically possible based on experimental batteries but it needs to be mass-manufactured relatively cheaply to make a mainstream EV