I think this is highly dependent on the company. I've worked at a few of the top few tech cos as both an engineer and a product manager, and I don't recall working closely with anyone who came from consulting, although there are probably a few. A handful have MBAs, some come from engineering, some have weird liberal arts degrees. It's a very diverse group of people in my experience. It can be a good career path for engineers who are more excited about the problems they're solving and the people they're solving them for than about the raw technical challenge.

Upward mobility is also highly dependent on the company. I've found some companies to be more product-driven, and some to be more engineering-driven (e.g. goog). Upward mobility for product managers is obviously better in product-driven organizations.