I'm a big fan of the Bleach manga by Kubo Tite just because the author always seems to find a curve ball to throw every time the story gets a little bit boring. While the revealing of new interesting things always makes the moment before presentation very intense, the presentation itself hasn't always been as good as you'd expect.
This time, Kubo reveals that there's a final form for Ichigo's ultimate strike, the Getsuga Tenshō. Fans have been discussing various ideas regarding this and I'm going to discuss my own ideas and what I think about this and what other fans are thinking.
First of all, there's the big question if this final form will be able to kill the main antagonist, Aizen Sōsuke. Most people think it won't. But here's what I think. I think it will at least bring Ichigo's combat level up just enough to be able to defend from Aizen's non-special attacks. The community seems to think that Ichigo might be able to scratch Aizen with his new power but I'm pretty sure he won't be able to do anything like that very soon. I know because, even if Urahara was able to scratch Aizen before, he was able to do that because Aizen stopped fearing any attacks, thus stopped defending himself after he acquired the Hougyoku's power. While his defense wasn't as "in-humanly" strong as he appeared, his offensive powers were clearly demonstrated when he took down Urahara, Ishin and Yoruichi-san in virtually one blow (taking all that previous damage only helped to show how much above the powers of those three he is). Of course, there's the idea that Aizen isn't that strong and instead is using his zanpakutō's total-hypnosis ability to manipulate what everyone around him perceives but I think that's a bit far-fetched. If he wasn't so strong, it wouldn't make sense that his zanpakutō's power is absolute and if that was his only power, the majority of fans would stop liking Kubo, for sure.
Then there's a big disappointment because Zangetsu is so cool and everyone thought he will be the one to teach Ichigo all about his powers but instead, Kubo decided to let Ishin, Ichigo's father teach him his ultimate attack. I think there's a big catch here: a chapter or two earlier we see Ishin perform a very powerful Getsuga Tenshō (as he called it when he fired it) in shikai form (if were are going to assume Ishin's zanpakutō is always in shikai form like Ichigo's and doesn't have an un-released form). Ichigo doesn't seem to notice this or he does but doesn't want to ask his dad any questions like he said to him when he first arrived on the battlefield where Aizen and Ichigo were. In any way, Ishin's Getsuga is nothing like his son's so no-one should confuse them. If you want to know why, it's simply because Ishin's Getsuga resembled a slash from a sword many times bigger and the entire mass of reiatsu was evenly controlled while Ichigo's Getsuga can barely be controlled when it's bigger than his sword. He either shoots a center mass that drags the rest of it along like an air bubble surfacing from water or he shoots a fast blast as long as his sword is but has minimal effect as seen so far.
So I think Ishin might teach him the technique but in the end it would be very different from his own. Well, at least that's what I hope.
And a bit about my own ideas. Aizen says to Ichigo at one point that he will be back to eat him. This is very interesting since Aizen looks a lot like a Vasto Lorde or some sort of perfect hybrid between a shinigami and a hollow's souls (and we know hollow eat other stronger hollows to evolve). Actually, he looks much like what Ichigo looked like just before his reiatsu covered him when he transformed into a full hollow in his fight with Ulquiorra or right after he turned back to normal.
When Aizen "tastes" Ichigo's reiatsu from the first slash he received from him, he seems to realize that Ichigo's reiatsu changed after fighting Ulquiorra but doesn't say how exactly, he just acknowledges that he seemed to have acquired an even greater power than that which he expected him to have acquired so far, feeling pleased about the fact (remember that Ulquiorra said Aizen didn't know of his second resurrection form).
It would be great if Aizen's new form is nothing different than Ichigo's new form. It would provide good closure for the manga. But Aizen has always been smarter than everyone else so it's hard to imagine that he wouldn't know about this. This idea could also be flawed, since in the last chapter, Aizen somehow destroyed the "soul train" that resides between the real world and the spirit world where shinigami live. The creature was supposed to be untouchable by shinigami, living in a world of reason, untouchable by reiatsu-based beings. This could only mean that Aizen acquired some form of higher reasoning or understanding which kind of contradicts hollows (though, not shinigamis). If he is both a hollow and a shinigami then it could mean that his powers are hollow and his reasoning is shinigami but that's all just non-ending discussion.
I'm going to stop here because there's too much to talk about and I don't have any feedback yet. I'm only going to tell you another one of my ideas: what if Ishin is a vizard as well as Ichigo? You wonder why I think this? It's been clear that the Vizards have been hiding something from Ichigo and at the same time they wanted him on their team and they place all their hopes in him. I believe they tried recruiting Ishin too. But when did Ishin become a vizard? Well, doesn't he and Urahara seem rather close? ;)