There surely are limits, but I don't think we have a good idea of what those are, and there's nothing to indicate we're anywhere close to them. In terms of raw facts, you can look at the information content and know that you need at least that many bits to represent that knowledge in the model. Intelligence/reasoning is a lot less clear.

100GB to 5GB would be 20x. Video has seen an improvement of that magnitude in the days since MPEG-1.

It's interesting to consider that improvements in video codecs have come from both research and massively increased computing power, basically trading space for computation. LLMs are mostly constrained by memory bandwidth, so if there was some equivalent technique to trade space for computation in LLM inference, that would be a nice win.