If I understand properly how SMT works, this can good and bad at the same time:
- More companies, more sites, more money in it, more traffic.
- Steemit userbase might look around on the new sites too and spend less time on Steemit.
- Competition among SMT sites which leads to the urge of improving faster.
This shouldn't really effect Steemit in a bad way. But if it does, then there will be one(or more) site(s) that will be a better version of Steemit. Don't forget that Facebook wasn't the first social network. :)