I know this'd be a fairly boring answer to Aizen's "big revelavtion".
But is it possible that he was going to say half human, half shinigami?
Two things make me consider this;
1) In this chapter he says "Because you are a human and a-" as opposed to "a shinigami and a-", so perhaps last weeks was a mistranslation?
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2) On that same page linked above, Ichigo says: "I was mistaken though. I had no need to hear them from the start, since the answer appeared immediately before my eyes."
Which is followed by Isshin's appearance:
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So perhaps he meant "it appeared before my eyes", in the literal sense. That his father appeared before his eyes, a shinigami. And you have to remember, up until this point, Ichigo's had no knowledge of his dad being one.
Just a thought. I'd be a little dissapointed if that actually is what Aizen meant, but still, it's a possibility, no?