The reward pool decreases over time, yes. Of course, doesnt that mean that a scarce resource will increase in price?
Do not forget, STEEM is required for bandwidth. Where are popular applications going to get the STEEM to provide their users with enough bandwidth to interact and for their sites to grow.
Yes, as the reward pool decreases the value of steem should increase, but isn't that even more incentive for those with lots of steem to just use it to increase their profits without increasing the quality of the content? If you think of steem like any other cryptocurrency, then that is probably ok, but if steem is supposed to be rewarding based on quality, some serious changes need to be made around here.
I think the model is changing as I wrote in my latest post. Those with STEEM are starting to delegate to different projects. It is the projects that are doing the upvoting.
And all in all, the larger accounts do not create a ton of content. Look at the top 50 accounts and you see they rarely post...a couple times a week at most.
As more newer people come on, collectively the larger accounts start to lose their power since a larger portion of the reward pool goes to the content creators. We already saw a big shift the last year. I expect, when more people sign on in bigger numbers, this will even be more pronounced.