There's something bugging me... Allen's innocence still part of his body, right? With the 14th begining to awake, there's a possibility of the innocence stop activating? Or perhaps turn itself against Allen? It self activated before to kill Mana, be I don't know if will activate against a Noah (because Mana was an Akuma at the time).
Personally... I don't think Allen's Innocence will activate against the 14th. Innocence seems fairly sentient, and I think it would be more concerned with keeping its host alive, especially since Allen still wants to fight for its sake. If Allen's heart changed, then I could see it turning him into a Fallen (or trying to), but there's no indication that it will, even with the 14th in the picture. After all, both oppose the Earl.
And I guess that by cohabiting in the same person, the Innocence and Dark Matter would have developed some sort of resistance to the other. In him, anyway. Although maybe as the latter spreads, Allen will end up in pain or something.