as i heard there was idea what tokens will be able to be buyable via bitcoin too, so steem can be not so liquid , also i think sbd can be used too. Of course because steem is limited and reward pool is limited because of that it will be harder and harder to earn more steem, but there might be some changes and hardforks to algo. I just hope we will evolve and adapt more , because right now steemit is still in beta and need a lot of work to be done.