I think one of the biggest pre-requisites for autonomous driving will also be vehicle to vehicle communication. That is a key aspect that cannot be overlooked. An autonomous car cannot exist as an independent entity in the real world, imho. It requires all the sensors to decode the environment presented to it yes, but the environment (cars, roads etc.) needs to give it significant amount of localized data for it to maneuver through safely.
And V2V will become a leveller because cars from other brands will have to communicate using the same protocols. That said, smaller improvements (as mentioned by OP) will definitely arrive beforehand but don't expect to sleep when your Tesla drives you around and wake up, soon.
Converting from one technology to another is always a bigger problem than when the entire world is on one tech. The big headache that has to be dealt with when designing an autonomous car is it being the only autonomous car on the road. An autonomous car in a fully connected driving environment is a simple problem by comparison. It is 100% vital that problem is solved because it's going to be decades before it will be possible for every car to be autonomous and accommodations still need to be made for classic cars owned by hobbyists.
The average car in the United States is 11 years old and the fleet is getting older every year. That means 1/2 of the cars on the road were built before 2005. I've been driving a 24 year old car until recently. Requiring people upgrade their car would be a massive burden on the poor. If someone lives in the core of a major city, public transportation is usually fair to excellent in a few places, but get outside the city core and public transportation quality drops off a cliff.
When I lived in the Seattle area, I was a 1/2 hour drive from downtown Seattle and a 1/2 hour drive from Redmond (where Microsoft is) if I left at 5:30 in the morning. It was an hour's drive if I left any later. I looked at public transport options. There was bus service that picked up on my street, but it only ran a couple of times a day and only went to downtown Seattle. If I drove to the nearest park and ride (15-20 minute drive) and got a bus there, it would still take me 3 bus transfers and 2 hours to get to work in Redmond.
By Seattle standards, I lived "close in", but public transport was so poor, driving was my only realistic option.
Getting any further out from a major city and it becomes even less viable. There are people who work in the San Francisco Bay area and Los Angeles who live 60 miles or more from work. For most of them, there are zero public transport options. Most of these people live so far from work because they can't afford to live any closer.
The US also has a lot of rural areas where buses would burn more fuel than have people drive their own cars because the population density is way too low to make it worthwhile.
Autonomous electric cars in some kind of taxi service will help to some degree, but it's going to be a long time before there are enough cheap Ubers in rural areas to where the rural poor can give up their cars. Many will still refuse to because the rural poor also tend to be more conservative about adopting new technology than urban dwellers (most of time, there are always exceptions).
The United States alone has over 250 million cars on the road and worldwide production is about 80 million cars a year. Even every car built starting Jan 1 was fully autonomous and there was some sort of program to give poor people autonomous cars, it would take the US consuming every car built in the world for three years just to replace all US cars.
The autonomous engineers have had to deal with the assumption their car is the only autonomous one out there because that will be the reality at first and even many years down the road, there will still be "dumb" cars autonomous cars will have to deal with.