So much junk being spewed by people who are passionate about the hobby, but with no data to back any of it up.

What do we know?
Arcades are still basically dead. Pinball is even more of a ghost in what few arcades remain.
Barcades are doing well, but are geared toward the 21+ crowd due to their nature. Possibly a fad, time will tell.

The hobby has been increasing since the early 2000s. Today we have more vendors, more repo parts, and this has helped cause a surge in prices.

What we don't have are new techs. Probably one of the largest hurdles in this hobby is having a dedicated person you can call up to repair your broken machine.
These machines are complicated. It takes a lot of tools and knowledge to keep them running. This requires a passion on the part of their owners to invest time/resources.

What would be useful is a poll to show the age of various owners. My anecdotal experience is that the new blood tends to be mid 30s to mid 40s. These are the guys who have disposable income and also experienced machines as a kid. What I do not see are younger people. At 29, I am no spring chicken and I can only think of a handful of people I have encountered that are younger than me. Of those, many inherited their love of pinball through their father who collected which is a pretty small pool.

In 10 years you will see some of the people who got in during the late 90's early 2k's age out. Those machines will just get sold off into other collections. 20 years many of those dropping bucks now will be out due to age. There are things we cannot know now, but what happens when clive/john wart/rob anthony retire? What about Terry?

There are a lot of people that have enabled our hobby to flourish. No one knows who or if someone else will step up to replace them. If parts get hard to come by and boards cannot be repaired then the hobby dies. If the next generation doesn't take an active interest, the hobby dies. Anyone who thinks they know what to expect is dreaming.