I think the immediate events following Chancellorsville go about as planned. Lee advocates an invasion of Pennsylvania to gather supplies and give the residents of Virginia a breather (and, if they're very lucky, take some of the sting out of what's happening at Vicksburg). Longstreet and Jackson lead their respective corps on pretty much the same route as in OTL. Stuart still finds himself on the wrong side of a moving AoP and a surprisingly stout Union cavalry arm.
Gettysburg, in that area, is a natural army magnet, so there is a good chance that something happens there. It might end up being a less-than-general engagement (say, Jackson vs. I and XI Corps), and could easily end in a Confederate victory.
I do not think, however, that the butterflies are going to throw the campaign, let alone the war, to the Confederacy. Lee is still on the end of a very long, convoluted supply line, which proved to be very vulnerable in OTL. Meade still has a plan drafted to cover Washington by fortifying along Pipe Creek (south of Gettysburg). Lee cannot afford to forage too long in Pennsylvania - too many Union troops around, and more can be dispatched (not the best quality, to be sure, but Lee cannot ignore them). If you gave Halleck enough time, he could probably scrounge together a force to threaten Richmond without taking away from Meade. Further, Lee cannot resupply - or otherwise acquire - "powder and ball" fast enough to fight multiple battles.
So, the ANV will be forced, sooner or later, to return home. They might not come out any better than, say, 15,000 more men than in OTL. Even with Jackson, that's not going to be enough to make a difference come 1864.