The Incas would probably collapse at some point, but of course it wouldn't be the end of Andean civilization. There might be another period of dual giant Andean powers, like Huari and Tiahuanaco in the first millenium, Chimor and Cuzco before the rise of the Incas, and the realms of Huascar and Atahualpa during the Inca civil war.
What I'd be interested in is the further developments along the fringes of the Inca territory - The Incas brought their high level of Andean civilization to many areas which hadn't yet achieved such progress, like northwestern Argentina, northern Chile, and southern Colombia. Chiefdom-level societies such as the Diaguitas in Chile and the Chibchas in Colombia were on the verge of evolving into state-level polities.
As for the areas to the north, I'd like to think that within such a time span, the Taino in the Caribbean would start to build Mesoamerican-style city-states with growing influence from the mainland. The Taino could play a key role in spreading new ideas and technologies throughout the Gulf of Mexico.