My thought is that if millions of people relied on the blockchain for their primary income, to maintain a decent standard of living they would have to consistently sell for HIVE for some sort of currency they can pay the bills with, so the price of HIVE would decrease and users would have to sell more to make up the difference. The reason HIVE works is because of investing and staking, which requires buying and investing - not selling.
If HIVE were $100, and posts earned $400 - $1000, I could see many many people getting on board, posting and the standard of content would be highly scrutinized (like back in the steem days), which could have a positive effect on reputation. But it would also attract a lot of get-rich-quick people, only blogging with the intent of selling as soon as the liquid token is within their reach. If millions of people did this, $100 hive would not last very long. This is what I was getting at with supply and demand.
Yes the blockchain could potentially support millions, but the motive behind those millions would determine the value and stability of HIVE. IF their motive is to earn and sell, it would kill the whole thing, if their motive is long term investments (like many old-timers here), then it can continue to build and build. Many people associate crypto-currency with buy low / sell high = LAMBO.
I've been posting almost daily since 2017 and very rarely sell. At some point I will sell, but not until my time investment was worth it. Right now with current prices, I'm on track to make 4.2K/year. It's taken YEARS to get to this point. Hive would have to 5x before I would even consider cashing out. I can see $3.00 HIVE someday in the future... but by then the cost of living may be way higher and it's only a drop in the bucket, so to speak.