2-3 years away is a life time. They are already on deep doo-doo with their Model 3 production line problem, the article I linked to clearly shows they are loosing the heart of stock analyst. If the stuff (battery or whatever) is as far off as 2 to 3 years, they had to manage expectation better. They better get their ducks in a row.
Yes, with the Model 3, I dont know, why they have to reinvent the wheel. There are certain way to build cars, and they are doing their own thing, with welded aluminium and other fancy stuff. Which sounds nice, and then small repair jobs are more expensive than buying a new car from a different maker. And production is also complicated.
That is one of the reasons I'm still waiting for the electric car, and the expensive battery.
Right now, 30% of the battery price is formation and assembly. This can be reduced to almost nothing because you are creating high voltage cells with multiple electrodes inside. So imagine, that instead of the 3.7V cells, that needs to be individually balanced, filled, tested, graded - you get a 48V pack, something like the lead acid battery. Your throughput suddenly skyrockets. Also, energy requirement of the manufacturing is reduced drastically.
The way battery manufacturing formation is an extremely slow process, and it requires very large manufacturing setup. Because you need to charge and discharge the battery, individually, store it in a fireproof container, thousands at the same time, and cannot use high current, since it is not ready for that yet.
If you reduce the cost of the battery, the car becomes
very very cheap. Let's take the VW e-golf, as there is regular golf also. The e-golf is 30K, regular golf is 20K. I've seen 17K as the battery price. Halve that. Suddenly you have a car, which is on-par in price with the old ICE golf. And faster, and accelerates better. And if the government rebates are still in place...