Steem Power is no more than Steem and that's the single point of failure and where the actual money comes from. Money comes from fiat and btc and other cryptocurrencies into STEEM, that's what holding the whole platform together and creating the payouts. You already said SP is also inflationary (it's Steem after all too) so it doesn't matter if it keeps a similar price over 2 years, it will inflate either way and that's if you don't power down at all.
Bitcoin always went down because of fundamentals, it's all about fundamentals and sentiment in crypto, technical analysis is for the very short term. Bitcoin dropped when Mt Gox held most of the BTC for sale. Ethereum dropped from 21 dollars to 10 almost in a single day during the DAO hack.
Steem can't seem to find a bottom because traders and speculators are beginning to realize that unless you power up (which doesn't make sense to me but I can give you that some Steem believers will do) it's pointless to buy.