[Guido]

Have seen chapter 131 now.

Spoiler for Chapter 131:

Just speculation but the anime has given a faint hint that they'll be adapting up to the latest volume.

Where do I have proofs to state that hypothesis?
The shape of the Earl's new ark seems like a cube, whose components have not finished downloading.

If any of you is watching the anime and paid attention to the new opening, there's a shot in it that features Bookman, Marie, and Miranda looking up at a golden, luminous object at the sky which quite more or less resembles a cube.

This chapter has an alike page with those outside of the ark looking at the new ark at the sky.

If my speculation turns true in about five months, assuming that the producers would like to extend the anime for another three months, that would mean that the producers have already planned beforehand to follow the manga all the way

Now to discuss the chapter.

My! D.Gray-man manga is starting to look slightly alike to My-Otome anime. I mean the Earl uses this organ-machine device around the Egg to create the akuma bodies, and the only one who can shut down the machine is the musician and the key.
So to speak the elusive fourteenth Noah whom Cross mentioned the previous chapter.

And I now know how the puzzle pieces are falling to the places that they fit.

Is there a possible connection between Lenalee and Allen, since he visited her dream?

But what's more intriguing was the figure that Allen saw in Lenalee's dream.
And now I have reasons to believe that the hand that Lenalee saw in her prophetic dream did not belong to Allen, but perhaps the fourteenth?

But for a plot twist Cross pushes on that Allen's the only one who can shut the akuma machine, and what's more the shadow figure who stand before him at the hidden room mean that Timcampy is the key

Could it be that Allen is the fourteenth Noah?

Or may be that Allen is carrying something within him passed on by someone else previously?

I have read theories that Mana could have been or not a Noah; more specific the traitor Noah.

As of now nothing else has the manga-ka developed about Mana, save that he found and adopted Allen; resurrected back as an akuma by Allen; and just speculation that his soul (the skull) lives in Allen's cursed eye.

My draft hypothesis before next chapter comes is that Mana may have or not been the fourteenth Noah to awake in the story's present timeline, however, he died before the Noah powers manifested on him.
The Noah powers likely could have been transferred to Allen when the akuma Noah slashed his left eye; and the mana skull materializing outside of Allen's cursed eye during the fight with Eliade is the remnant of those powers, thus making Allen the successor to the 14th or specifically the new 14th Noah.

Pretty wild speculation I posted.