Yesterday, Hiroyuki Takei responded on Twitter to a fans comment about the Shaman King anime. Below is the original Japanese followed by an English translation from Dit on Tumblr:
Fan (@nooreneri): 懐かしい…！ 今でもシャーマンキング大好きです☺️ またアニメ化してくれないかなぁ…！
This brings back such good memories! I still love Shaman King, after all this time. I hope it gets a new anime someday!
(This fan’s comment is in reference to a recent post by Takei of Yoh Askura’s first Oversoul.)
Takei: じつを言うと本格的なところまで再アニメ化の話はありましたが…前作の声優さんや楽曲が使用できないとのことで、お断りさせていただきました。またチャンスがあるといいですね
Well, to be honest, there WAS going to be a new anime… But since it was impossible to keep the same voice actors and music from the first one, I decided to decline the offer. Who knows, maybe next time.
As of the time of this posting, there were 10,770 retweets and 5,089 likes. 
Hiroyuki Takei was most likely referring to the “music” as Starchild Records (as part of King Records) who produced the music for the original Shaman King anime series. Additionally, Megumi Hayashibara, who played Anna in the original anime, has her music label through King Records as well. While not impossible to have a new anime without her (or King Records), it definitely adds some additional issues to the offer.
It’s important to note that there are many offers made for adapting manga into anime. Additionally, multiple offers could be made from different studios or committees. We do not know when this anime offer was originally made as well, since this could be from many years ago.
Personally, I am happy that there are (or were) offers for a new Shaman King anime. But I respect that Hiroyuki Takei wanted to have some control over the direction of the adaption and that it would meet the quality that he expects. With over 10,000 retweets, I’d expect to help some traction on some new offers to be made.
