Not very upgradable. If you get an i5 or i7, you have no need to change CPUs as you have the best, but if you get an i3 you could upgrade to an i5. The GPU could be swapped but ONLY for a card small enough to fit. They use a small gtx760. I don't believe there are any better GPUs to change to besides an r9 285 (which might require too much power).
No matter what, you will void the warranty by even opening the case.