This is a Rumor!
This is NOT confirmed.
This COULD be false.
This wasn't from an extremely reliable source. (but it hasn't been completely wrong at times either)
Now that's out of the way, I present to you, the information I have come aross. All of which is rumors, that I am following VERY closely.
It's one of those "My friend's father works at Shueisha" rumors. So, they might have the same amount of truth as they do in the USA.
Before I get to that, let me explain a bit about Jumbor first. Jumbor has been cancelled in Japan with only 10 chapters. None the less, it was going to be printed in Volume form. Normally they are released in 2 Volumes, just like another series 2 weeks before Jumbor, got cancelled. That series is getting 2 volumes to release it's series. But, when Jumbor was orginally planned to be released, via Weekly Jump notice, in April, it was not on the release list. Now, just like with Shaman King Volume 32, you just don't assume that it was cancelled, it was just pushed back. Now we know that it will be released on May 2nd in Japan, with all 10 chapters in a single volume.
Now the rumor follows that Takei broke a deal with Shueisha from having 2 Jumbor Volumes down to 1. This is to allow him to make a "Shaman King: Conclusion" volume which will contain an alternate or extended version of the ending to SK. This has no set sale date, but to be assumed after Jumbor. More updates on when/how it will be released will be expressed in it's normal venues (normally Weekly Jump or in an ad in the Jumbor Volume). So, in about 4 weeks, we should be able to confirm or deny this rumor (or sooner, if it gets annouced).
So, again, it's all a rumor. We don't have any "official" document to confirm or deny this. BadS (who works at Mankin-Trad and The Great Spirit) and I will be keeping a look out for this story, and be posting updates as we figure it all out. If they is proven to be a rumor, I will request that this topic be locked to prevent future confusion.