If the trend continues and the Federal judges keep overturning bans and appellate courts back them up, this may never get to the SCOTUS (who tend to take cases where there is disagreement between lower courts). That being said, I suspect at least one Fed. Appellate court is going to hold up a SSM and my money is on the 5th Circuit (TX,LA,MS) which is heavily balanced to GOP nominees
Also, the gray and green states have no federal case. The Wyoming Supreme Court could strike down the statute ban though. Not sure about Arkansas.