Actually, it's not a problem at all. If EOS is pretty successful, steem could launch itself on EOS.

It's like this:

I built an app with some homegrown tools. Then webpack and react works pretty well. So, I changed my app to use them.

What matter is the steem community and what it does. If someone could do it better than steem, that's also good thing.

It's like we've twitter, facebook and many other social networks.