This question came up recently and I found this post in searching for an answer. It seems clear to me after reading Isa 65:20-26 that option 1 is out of the question and option 2 is closer to home. The 100yrs certainly isn't a maximum, and it doesn't seem from this passage to be talking about a set number of years at all. If anything 100yrs is a minimum. Reading this passage in the AMP is helpful. As was mentioned, It seems to be painting a picture of pre-flood like conditions, with the nature of carnivorous animals being changed and the lifespan of Gods people being compared to the lifespan of a tree.