I think we tend to overestimate the capacity of people to retrain for new jobs. Sure, in the example you brought up (auto to renewable energy), people moved from a manual labor job to a manual labor job, but what happens when we run out of manual labor jobs? What happens when we automate white-collar work? Will accountants, for instance, need to retrain to become programmers? Will manual laborers? I think that we'll eventually reach a point where we've made entire types of jobs obsolete, and thus made people who are only capable of being competitive in that field obsolete as well. Transitional labor, I think, is a deferment of the problem, not a solution.
Really a lot of white collar jobs are already automated. The example you use with Accounting is mostly capable of being run by much fewer people than in the past. As an example, many businesses used to keep a payroll department as a separate functional department within accounting. Now, if a businesses even handles their own payroll instead of outsourcing it to ADP or a similar company, they have many fewer people doing it. And ADP is able to handle with their small staff what could only be handled by a dozen people for a single company before. So you could argue that we're already well into the phase of automating white collar jobs as well.