I was thinking about this today so I thought I'd share.
If Nolan wanted to have an eight-year gap, why not do it during the film rather than before it. At present, having Bruce learn to be Batman twice in the same film seems a bit redundant anyway.
But if he was in prison for eight years that might give him time to recover from a back breaking while Gotham goes to hell, and Bane could really set up class warfare.
Plus doin it this way would make Modine's character make sense. Maybe have it so it takes place a few months after the Dark Knight, so when Batman comes on the scene to rescue the stock market people, Modine's reaction to having his men chase Batman would make sense. Him being so obsessed with getting Batman in the film was not very realistic after 8 years.
My friend think that the whole movie should have have held onto the theme of economic warfare rather than pissing away a few stupid references to it. It's exactly the kind of crime Batman can't fight because he and Wayne Enterprises had helped fuel the fires after all!