The war was fought for another two years (close enough) after this, because by this point only a total defeat of either side - especially the South, its leadership convinced in the righteousness of its cause - would have ended it. But from this point on, all the advantages were to the Union: they had finally gotten a semblance of military leadership under Meade (and later Grant) to fight the Virginian theater, they had the numeric advantage of troops (the South intentionally fought with less manpower because they needed to keep enough white men back home to keep the slavery population in check), they had the economic and engineering might (the South had foolishly stuck to a cotton industry dominance and failed to create enough ironworks and grain farms to supply themselves). This defeat combined with Lincoln's Emancipation Proclamation effectively kept Europe out of the war for good.
On an end note, a fellow Hordian Andy Hall runs the Dead Confederates blog (tracking southern and Texan history), and had his own take on the Second Day of Gettysburg from the memoirs of a Texan soldier caught in the thick of it. He's got a great blog: link it.