SPOILER
Aizen is actually the good guy
The bad guy is Ichigo's father. That's why Aizen want to destroy Karakura Town. The father was a hollow originally before becoming shinigami. That explain the innate hollowfication of Ichigo after he was killed. It was in his gene. The father have genjutsu more powerful than Aizen, that Aizen need more power from hougyoku to defeat him

geez, loosen up man
when i said genjutsu i mean the hypnotizing thing that Aizen have, at least you know what i mean. I know the genjutsu term is in Naruto and most people know naruto and know genjutsu too.

And no, don't ask for source, you just don't have a source of humour enzyme in your body. This is just my speculation IF Aizen is actually not a bad guy. I put SPOILERS there just in case this turns out to be true

there will be filler in middle of all this battle, unless they want to make it slow by adding things like haru2 interview in reborn. Captain Hitsugaya fight just started while the manga most recently just finish that battle . its not that far even though there's Ichigo's battle in the middle.

what twist?
they just put aside Ginjo like he was nothing but only for Ichigo to gain his power back
i thought the whole substitute shinigami deal was supposed to be the main issue
but mangaka went with a totally new enemy already, Ivan