Best Xenon CPU for After effects (big budget)

I would approach it another way; if you are building a machine that will only ever run AE, then save your cash on a top-line CPU and put it into RAM and drive space. An old single-Xeon board with 256gb RAM is almost certainly going to render faster than a dual board with 64gb, since AE has an attitude to memory that the most ardent fans of $5 buffets can only dream of.

If there's a slight possibility that you will run other things (3D renderers, Resolve/Fusion, etc.) then make your decisions based on those apps, because they have far more capacity to make use of high power CPUs, SLI, etc. but only in specific combinations. Some apps prefer high clock cores, others are massively multi-threaded. Some are all about the CPU, others are GPU-mad. In this case, treat AE as just as aside, it will chug along at its usual unimpressive speed on whatever you give it.

Adobe generally does not discuss plans in open forums... and anyone who is testing a new/revised program will have signed a Non-Disclosure Agreement

If Adobe is working on a program to take advantage of advanced hardware, nobody here will know until an official announcement is made

I am sorry to state this, but none of the Adobe Creative Cloud apps (that includes After Effects and Premiere Pro) take anywhere near full advantage of more than about 10 to 12 CPU cores - total. Worse, dual-CPU systems actually perform slower than single-CPU systems of equal clock speeds due to the huge additional latency that the second CPU entails. And to top it off, large portions of Adobe's program code are still only single-threaded, meaning that the programs as a whole still heavily favor high clock speeds over high core counts.