To be clear, the amount of SBD being printed is only dependent on the price of Steem.
If the author rewards for a post are $100, and Steem is worth $1 USD, then you'll get 50 SBD. If Steem is worth $3 USD, then said post will be worth $300 and release 150 SBD.
Posting more does not increase the amount of SBD, as the pool's size is constant. It only changes its allocation between different users.
Though yes, SBD mostly has a downward pressure, though I wrote an interesting piece on why an increase in SBD's supply could be a requisite condition for its price to go up, though that's slightly longer term.
I agree @geekorner that the rewards pool is constant. But when a few people have a large number of SBDs and when they flood it into the market with a cheap price, the price of SBD is bound to drop.
But if the same number of SBDs is well distributed, a lot of value will be preserved.
Also, The Steem price is massively increasing the number of SBDs like you said.