So, the question is pretty simple. What if the Inca Empire survives. Preferably at it's territorial height (maybe even larger). Pizarro's company was extremely small, and honestly if he had not had the help of native factions, he and all of his company would have been slaughtered.
So, if Pizarro is taken care of early on, that hopefully buys the Inca enough time to recover from the small pox epidemic that had really ravaged them. By the time a full fledged Spanish expedition is set against them (which would still be quite small) I should think that the Inca could wipe them out easily, but only if they remain unified. Afterall, the Inca could produce massive armies of 80,000 and the Spanish at most would send 1000 men. AT MOST.
So how does a surviving Inca Empire look? Eventually they would adopt steel and gunpowder from trading with Europeans. Horses even. I could see the Inca expanding their fingers into the rainforests as slavers trading to the Europeans, and possibly becoming a Pacific naval power if given the time.
What do you think? How can the Roman Empire of South America make it?