There's an Internal Market on Steemit already. Currently it has only Steem and SBD pairs, but with SMTs incoming, we'll probably see a full fledged market. That said, I don't see Steemit getting into fiat or BTC exchanges - there are enough exchanges that do that well.
Marketing is of course key.
Steemit apps for Android and iOS are in development, and due a release soon.
I am looking at a direct exchange where steem/sbd will have a direct autonomy of exchange to local currency instead of converting to bitcoin before eventually turning it to any local currency or probably using it to buy goods directly.
It is possible to create SMTs along the tether or openledger (from bitshares) model where placeholders (IOU) for fiat, BTC, etc. can trade on the internal market once SMTs can. I don't see Steemit Inc doing it (though who knows for sure), but it doesn't have to be them, anyone else can do it such as blocktrades or a new player.