Since cars have a 10-20 year lifespan, and electric is becoming superior, that will probably solve itself over the next 10-20 years (maybe they'll be EV powered by natural gas for a while, but that's still a win, and then the grid might get greener.)

Aviation fuel is the highest and best use of hydrocarbons (along with some chemical production), so we can deal with that last, after lots of power generation, demand reduction/efficiency, etc

Airliners have gotten far more efficient over the last 40 years, starting with the 757/767. (The 757 design got its start from more efficient engines and a new wing shape.) In fact, efficiency improvements are the primary factor driving new airliner models and sales. At the time of the 757 launch, fuel was 40% of the operating cost of air travel.

A huge improvement (for the biggest planes) is going to twins and ETOPS (not just fuel, also maintenance cost, but also fuel). Not as relevant to domestic routes, though.

Not sure your math checks out. EVs are < 1% of fleet and < 2% of sales in the USA. As you say, cars last 10-20 years and this number is rapidly getting longer. Vehicles older than 16 years are the most-rapidly-growing segment of the US vehicle fleet. The average age of US light passenger vehicles hit 12 years in 2016. In 2020 there will still be 80 million cars on the road that were built 1995 or earlier, none of which were electric or even hybrids. Virtually all of the cars sold this year will still be on the road in 2030, and 98% of them will be combustion powered.

What matters is miles driven, not number of vehicles. For someone with a 1-2h each way commute (sigh), replacing a 2010 truck with a 5-year-old 2025 EV in 2030 will make sense on a 2 year cash return basis. For someone who drives 1-2k miles/year, it probably isn't worth upgrading.

Yeah but EVs make up a far smaller proportion of miles driven than they do the fleet by units. For obvious reasons: many EVs are short-range vehicles and the people who buy them are self-selecting as people who are both environmentally conscious and able to live with the range problems. People with long commutes who can't afford a Tesla are obligated to burn gas.

It is reasonable to assume that a 5 year old EV will be as cheap in 2030 (2025 model) as a 5 year old EV is today (2014 model), while becoming more capable at roughly the rate we've seen so far. A 5 year old Leaf is $6-10k now, and would be a ~250 mile range car by 2025.

Plant a lot of trees using the rail money?