Pretty sure this has absolutely nothing to do with Deepseek and even local LLM at large, which has been a thing for a while and an obvious use case original Llama leak and llama.cpp coming around.
Fact is Mac Pros in the Intel days supported 1.5TB RAM in some configurations[1] and that was 6 years ago expectations of their high end customer base. They needed to address the gap for those customers so they would have shipped such a product regardless. Local LLM is cherry-on-top. Deepseek in particular almost certainly had nothing to do with it. They will still need to double their supported RAM in their SoC to get there. Perhaps in a Mac Pro or a different quad-Max-glued chip.