Yes for thread pools instead of forking (could be process pools too). But that's only scratching the surface. It's how you communicate with those threads and allocate their work that makes the difference.

I think the quick and dirty answer is yes, although I doubt I would structure things the same way as a normal thread pool.

If you think about the heart of the problem, it is really synchronization, and that only needs to happen in certain places in programs. Anything you can break up into pieces that can be transformed independently can be leveraged for concurrency, which also implies that independent stages in a pipeline can be concurrent as well.