Certainly at current prices being a FTS isn’t viable.
But if/when Steem passes its ATH and stays there it would start to be at least plausible in some cases. Even then though, probably only a tiny number of accounts managing to live off of author rewards. But those with a reasonably large stake might then be able to earn enough to get by from a combination of curation earnings, delegation earnings, and fees from RC leasing. At least for those living in places with a relatively low cost of living.
But for the foreseeable future, consistently powering up rather than selling is compelling. And buying some Steem here and there for the long haul.