No, it's not!
NOT until Boston wins the World Series. What the heck do these people think the "1918" chant is about?!?
The point of The Curse is that Boston will not win a World Series, not that they won't ever beat out the Yankees at the end of the year. There have been plenty of seasons since 1918 that Boston came out ahead of the Yanks and even appeared in the World Series (to lose). If The Curse wasn't over then, it's not over now.
If they win next week, the curse will be over, but not before.