This is really not a valid argument. The grid is constantly being adapted to changing loads and if this 10% arrives, it will not arrive overnight. It will come on gradually and can be dealt with seamlessly.
And in some ways, elec cars could make life easier for grid management. Presently there is a big difference between daytime load and night time load. This requires utilities to daily start and stop large generators, and generators do not like this. Since most car charging will presumably occur overnight, this will tend to flatten the diurnal load curve, and that is a good thing.
Also, charging stations can be linked to the grid in a way to shed the charger load if system load gets too high. Good for the grid, not so good for someone that wakes up to an uncharged car!!
Similar to the issues that come with wind and solar inputs to the grid. These change the issues with power distribution, but all the issues can be worked with. In high solar areas, cheap daytime car charging. In wind areas, cheap car charging when wind is strong.
The grid is not a static entity. It adapts as needed. Slowly, indeed, but the changes are slow too.
I could see myself going with an electric car. Heck, folks around here are doing local trips on golf carts.
I could easily do 90% of my trips in an electric car that had a range of 100miles.
Not going to splurge for a Tesla. Not getting a golf cart. But something in between, could be appealing.
All comes down to batt tech, which is seeing incremental (slow) improvement. I think there are physical limits to storing electrons in a chemical medium, there may be a hard wall there somewhere. Or maybe there will be a step change in tech that will blow our minds. Who knows!!