I don't know about 50, but I'll make one: the limiting factor on the widespread deployment of self-driving vehicles will turn out to be vast numbers of unemployed drivers protesting by blocking roads and staging violent attacks on self-driving vehicles. This will be resolved by introducing a tax on self-driving vehicles, the proceeds of which will be used to employ former drivers to work as security guards to protect self-driving vehicles against attacks. In the end, the economics will self-stabilize so that there are just enough people attacking self-driving vehicles to justify the continued employment of the remainder as security guards. The net effect, if you do the math (which no one will) will be that driving will end up being 50% more expensive than it was before on an inflation-adjusted basis.