Negima! fan Hata reported a couple of things from Akamatsu-sensei's recent tweets. Here's the first tweet in question.
Basically, Akamatsu-sensei is answering a question posed to him on whether his next manga series will be published in Weekly Shounen Magazine or not. Akamatsu-sensei's answer confirms that he's no longer exclusive to Kodansha, and has a new editor.
The next two tweets are about Akamatsu-sensei having all of the original, manga materials for A.I. Love You, Love Hina, Negima!, My Santa, and another short work he did shipped to his home.
So, what does this mean?
Well, it would seem to explain the timing of Akamatsu-sensei's ending of Negima! When he recently posted on Facebook about the manga not being "truncated," I'm told that this is most likely the English term used by Sensei to indicate that the manga was NOT canceled, rather than it ending just as he planned.
Another popular theory is that Akamatsu-sensei is not happy with Kodansha, in light of the movie's poor showing at the box office. I'd be unhappy with SHAFT personally, but that's another issue. Besides, with the language barrier and nondisclosure agreements in place, it will be difficult to know the truth here. However, Akamatsu-sensei does have all of his original materials now.
Considering that Negima! will end in time for Golden Week, Akamatsu-sensei will get to take an actual vacation, and I'm sure his wife will be happy about that. ^_^
At this point, until we see how Negima! ends, it is impossible to really speculate on whether there will be a new Negima! series or not, to be published on Akamatsu-sensei's J-Comi site. Whether there is another Negima! or not (and frankly, with all the side-stories out there which could use a telling, I wish he would put some new, Negima! materials out there), I do think his next work could well end up on J-Comi. It would be an opportunity for Akamatsu-sensei to have complete control over his product, and allow for officially sanctioned English versions to be put up. I think that it shouldn't be too difficult for Akamatsu-sensei to have book publishing deals to allow for tankoubons to be printed in Japan and manga books to be published everywhere else.
As I am reminded, Akamatsu-sensei's lack of an exclusivity contract doesn't necessarily mean that he'd drop all ties with Kodansha. It may be that Akamatsu-sensei wants to shift to a monthly title, thus lessening the stress on him and his staff that a weekly publication has been putting on them. So, his next title could be published in one of Kodansha's monthly manga magazines.
Regardless, things are seemingly becoming clearer now on why Negima! *HAD* to end now when it appeared that the manga story could easily go on for a few more years.