First off. There is no way his Bankai is going to be sealed. Let's say they did not develop a method of stopping them from sealing Bankai, still the Captain Commander and Ichigo's Bankais are too similar. Remember, they could not take Ichigo's. Therefore, they can not take Yamamoto's either. And it's not just in appearance. They are EXACT opposites of each other. One is the sun, the other is the moon. Kubo didn't write out every small storyline first. He probably came up with the idea of two heroes first. Try and recall what Zangetsu's powers are, and what you read them to be on the subs. Therefore, neither of them will lose their Bankais. IMPOSSIBRU.
Aizen is not connected to this fight. He was an idiot anyhow, who thought that he could conquer everything himself. Juha Bach is much more noble than that. He is trying to reclaim glory for a race of people, who were almost obliterated by the Shinigami, who includes Aizen. Also, whoever thinks that Aizen is connected to Urahara is crazy. I saw this on another forum. No way. GTFO.
And we have seen West, East, and South so far. He is trying to end it fast, so he doesn't kill everything a long with himself. His own power is probably eating at his own body, just like it does to Ichigo. The other Shinigami don't experience that because their reiatsu isn't compacted into their bodies, they act as an extension of their soul slayer.
I wouldnt forget about Ichigo yet either, he still has a huge part in this fight. If yama's fight keeps going he might stop using his Bankai in order to save everything, especially if Ichigo shows up. Either way this manga is probably coming to a close after this battle. That's why they aren't showing the Anime of it yet. After this battle their isn't much left. We will never see some of the Captain's Bankai's if they don't show them soon. And some of them don't even like fighting in the first place.
But we will see more of Urahara and Isshin too. At the beginning of the anime Urahara agrees that they will probably not die an easy death. That wasn't only said because of what Aizen was doing. Urahara and Yoruichi are old. They've known about Juha Bach as well. And Isshin will come out to help Ichigo, or maybe not. Im not certain of it, its just one of my hopes, because father and son having the same Bankai would be great. If Isshin is coming back, he would use Mugetsu and relinquish his powers again, because he really doesn't care for them anyhow. Even though Urahara can't enter, we don't know if Ichi's father will be blocked from SS.
Im really excited for the rest of the Manga, but remember, nothing bad, except possible death because of his reiatsu, is going to happen to Yamaji. If it did, I would be very surprised.