I'm talking about content rewards. If, say, steemit now gives 100.000 USD per day for content creators to 10.000 users, that's 10$ per day, per user, on average.
If userbase escalates to 100.000, then that's 1$ per day, per user, on average.
If userbase escalates to 1 million, then that's 0.1$ per day, per user, on average.
A price rise can increase the rewards but the price curve can't compete with booming adoption curves. So naturally, rewards per author go down and "difficulty" in getting proper rewards when blogging, goes up. This has already happened. It is already more difficult right now to blog and get rewarded than it was in June or May. And this "difficulty" will increase as time progresses.
One aspect that I didn't think about until I was reading your reply is that as the user base increases, so will the number of people with moderate size wallets (dolphins). These new users will have the effect of spreading around the wealth if they behave independently and up vote subjects of their interest and not just popular content. So it should be true that the $ per user per post should go down, it will actually serve to more equally distribute the available steem. But again this all depends on the behavior of the new and existing steem users.