If being the magic word...
The world is so ripe for the next big language to be Scheme.
Why do you say that? Scheme is not new. Something radical would have to happen to make it popular out of nowhere.
Scheme is positioned to be that next edge to cut with. It's very much like Python and Ruby, with similar usage properties and library distribution practices. But at the same time it's got a simpler core and a more powerful syntax layer.
If we can just get people to stop discriminating against parenthesis and maybe get a nice web framework and a good deployment tool, we could see an explosion of usage in the Scehme world that inflates the space much like what happens with Ruby.
I yearn for the day when using Scheme professionally is No Big Deal.
What's necessary is for something very practical to require scheme. Ruby would still be a hobbyists language if Rails didn't come along. Perhaps arc could help here in the future but even the scheme community isn't totally amped on arc and therefore not rallying behind it.
Erlang seems better suited to be the next big lang than scheme. It has already found it's way into some of the big names like facebook and amazon, demonstrating practical importance, while solving problems that are still hard in other languages. cough concurrency...
This rift and indecision in lisp implementations only exists as long as we continue to allow it. If people just start hacking and using a system in larger numbers, it'll grow. The world is so ripe for the next big language to be Scheme.