The grid is more or less at capacity now.
If you made all the central heating electric and all the cars electric it just couldn’t cope.
Not strictly true, we’ll just move towards smarter grids.
At the moment they assume that not everyone wants a cup of tea simultaneously, so the grid doesn’t need to generate enough to power everyones kettles.
Substitute kettles for heating your house and you have a problem because everyone wants ~3 hours every morning and evening, and they’ll overlap. Same for charging your car. But if the grid could control those things. and heat your house up earlier, or charge your car at 4am rather than 6pm then it can shave the peaks off and can be much more efficient (in terms of infrastructure use).
An average sized house with solar panels on the roof will generate more than enough energy for it’s own consumption, we just need the infrastructure to use that during the daytime (e.g your car charges at work whilst the suns out, then you drive home and plug it in, but it powers your house).
I doubt it will happen in that timeline.
There isn’t a replacement technology and the issue of fuel poverty will scupper it
Air source heat pumps are pretty much the same cost as gas boilers.
People with solar panels and tariffs which measure generation rather than export can effectively run them for free on their panels too.