What's hard is cracking into the very, very top tier, the C++, C#, Java, etc. tier. I am also increasingly of the opinion that it simply takes massive corporate backing to get to that level, based on the observation that I haven't seen anything get to that level without it. Python's the only one that has arguably gotten there, I think, and it's still debatable.
That said, I do think that if you want to make a new language right now and really see it take off, you do need to find some problem that isn't well-solved, or come up with a reeaaalllly novel combination of things that didn't exist well before. It seems to me that this project is going to be shadowed by Haskell in a lot of ways.
But that's only if you want to see it take off. Not all languages are put out there with that intent.