It's impossible that this wasn't already considered during the design. We are not given multiple hundreds per cent per year in SP for the lolz. If that happened (increasing SP), and if the price didn't drop, it would be a sure-bet where everyone simply multiplies their money, 300-400-500-600% per year.

The fact that in a year I'll have, say 20-25k SP instead of 5k, is an admission that the price will be diluted and the investor will be compensated with more SP.

They could have made it deflationary, in the sense that there is a fixed pool of shares and all users pay over a year 10% of their holdings in order to pay witnesses, content, etc. But then you'd have accounting issues with exchanges and people saying they lost coins. But it would be the same thing more-or-less, except for people's perception that "we are going doooooooownnnnnnn".

The current design isn't without problems either: I don't think the reverse split option in a couple of years will be without a hitch. Doesn't this create problems for investors, exchanges etc? You'd have to completely rename the token for all people to be (forced to get) in sync and don't do something stupid like thinking "oh price is unbelievable right now (after the reverse split), let's sell". But that's ahead of our time.