What we really need are advances in battery energy storage.
They'll happen but it's going to take time. The good news is that batteries are already more than good enough that we could switch many/most cars from ICEs to EVs today with only modest changes to habits and infrastructure. Basically if you have a garage and don't need to routinely travel longer than 200 miles in a single trip, you can switch to an EV today.
No more IC engines, and cars can be redesigned from the ground up better using space that the engine, fuel delivery, and exhaust systems once took up.
I don't think ICEs will ever go away completely but I can see a day when they are a rarity or at least a minority. That's going to take a few decades to get to however. There are some use cases where ICEs just make more sense than pure EVs. But even the ICEs that remain I think will mostly be electrified because it will make economic sense to do so.
If we can get the energy per unit volume within an order of magnitude of gasoline, propane, or other fossil fuels, transportation would be radically changed.
You are measuring the wrong thing. What matters is usable energy/power per kilogram for the whole drivetrain. You are making the mistake of comparing the energy content of a volume of gasoline with the energy content volume of a battery but that's a flawed comparison. Gasoline is useless without a very large and very heavy engine to turn it into useful work. Just using the volumetric energy content of gasoline doesn't tell you anything really useful because the liquid does nothing by itself. You need to know how much the whole system weighs, how efficient it is at turning that energy into useful work, and how much it costs to do that. While there are some limitations and caveats, existing EVs today already have substantially better fuel economy for a given power and weight output for a wide variety of use cases. My Chevy Bolt EV has more torque than my pickup truck, vastly better fuel economy, comparable range (about 238 vs 275-320 miles) and only weighs about 300kg less. A Telsa Model X actually weighs more than my pickup and has more power, more torque, FAR better fuel economy, comparable range, etc.
And the good news is that battery technology is going to continue to get better. ICE technology is close to as good as it will ever get. An ICE produces more heat than it does useful work and there is no way to change that. Given that EVs are already matching or exceeding ICE performance in many cases and have lots of room to improve as battery tech improves, the future seems dim for ICEs in the long run.