Say I patent my invention and 2 years later I have a huge breakthrough that drastically improves the overall design (like putting wings on a tiger). Would the patent still stand, would it need to be updated, or would you need to file a new patent altogether?
It doesn't matter for the old patent. Improvements not described are not protected (unless encompassed in the old claims if they are broad).
You can file a new application and the old one would be prior art.
The patent system only cares about whats in your final application, not about what your actually build. It only protects whats in the granted claims, not what you're really doing.
Which is why there are always so many patents per technology - people are patenting improvements. It can even happen that somebody patents a non obvious improvement which they can't build because it would infringe your patent. Then you can't build that improvement because it would infringe their patent.