مؤمنين means Believers, not Muslims. A Believer is higher than a Muslim:
[049:014] The Arabs said, "We are Mu'mens (believers)." Say, "You have not believed; what you should say is, `We are Muslims (submitters),' until belief is established in your hearts." If you obey GOD and His messenger, He will not put any of your works to waste. GOD is Forgiver, Most Merciful.
Like I said brother, in theory and principle, everyone is expected and can be a Muslim. But again, this is a topic that is well beyond our earthly logic as I explained above.
I hope this helps, Insha'Allah.
Take care,
Osama Abdallah