It seems unlikely to me that it could be thousands of people, given the correspondence had with various people it seems likely to me that a few people have information that could lead in the correct direction. But I guess we'll never know.
The world is a big place. It's likely that in 2008 thousands of people had the right skillset to create Bitcoin, any one of which might have done it.
As long as Satoshi wants to stay hidden, we're not going to find them.
Even if he always used TOR/anonymous IPs, when accessing his @gmx.com account, with the number of sign-in's he had, it must be an absolute certainty, that he want through rogue exit nodes or some other de-anonymization methods we are not aware of, but deployed by gov. agencies.
This is my assumption. It's too critical a question to leave unanswered, from a national security perspective.