Someone buying 1 steem today for x BTC should expect to be able to sell it a year later for x/2 BTC, all other things being equal. The intended inflation rate is 100%. The US inflation rate us usually around 2-3%.

See the whitepaper: https://steemit.com/steem/@liondani/steem-whitepaper-download

Search for 100%. However, not all other things are equal with STEEM. The whitepaper argues that since 9 out of 10 newly minted STEEM are re-invested into STEEMPOWER, the perceived inflation rate will be much lower. This will have a large effect and it's likely that the market price will be higher than x/2 a year from now, maybe even >x. All other things are not equal with STEEM because of that, and because of the massive influx of the rest of the population expected in the upcoming years.