It won't happen within a day, but it will happen within a few years. Significantly shorter than a typical working life. The approach "we don't hire new drivers and the old drivers will retire eventually" won't work.The acceptance of the concept, the changes necessary within the company, feasibility outlooks, infrastructure changes, ....
Something such as driverless trucks won't happen in a day, but like most things the penetration takes time.
Sure, you keep the loading/unloading business, but how much time does that need compared to driving?
Unless you suggest the industry will do price rigging, I don't see why it would be expensive. The hardware costs a few hundred dollars, add generously a few thousands for the installation and the software. A vehicle that can drive 24/7 (apart from loading/unloading) can probably replace at least 3 drivers. Even if self-driving would cost $100,000, it would be a great return of investment.I don't share your optimism for the prospects of driverless cars/trucks because I don't think it will be that easy/cheap to retrofit existing vehicles and if it is easy and cheap, then it's too cheap and companies will simplly charge more money for it due to supply and demand.
Driverless trucks and taxis are just one example, many more will come at the same time.
Precise numbers? Predictions are hard, especially about the future. But it looks like it will happen more rapidly than in the past. And it will happen more complete - with most low-skill jobs being replaced.