The main thing that makes me suspect we might have AGI before 2100 are neuroprostheses: in addition to bionic eyes for humans, we've got working implants that replicate parts of hippocampal and cerebellar function for rats. At least one computational neuroscientist that I know of has told me that we could replicate the human cerebellum as well pretty soon, but the hard problem lies in finding suitable connections that could be used to interface the brain with computers well enough. He was also willing to go on record on neocortex prostheses not being that far away.

If we did have neural prostheses - the installation of which might end up becoming a routine medical procedure - they could no doubt be set to also record any surrounding brain activity, thus helping reverse engineer the parts we don't have figured out yet. Privacy issues might limit the extent to which that was done with humans, but less so for animals. X years to neuroprosthesis-driven cat uploads and then Y years to figuring out their neural algorithms and then creating better versions of those to get more-or-less neuromorphic AGIs.

The main crucial variables for estimating X would be the ability to manufacture sufficiently small chips to replace brain function with, and the ability to reliably interface them with the brain without risk of rejection or infection. I don't know how the latter is currently projected to develop.