The new M3 MacBook Pro M3 Max can have 128GB Ram (for a price...)
Finally after 13 years, they've caught up to the 128GB possible in a Mac Pro (though I've heard the 5,1s can push to 256GB...)
Hold on another 5-6 years I think, then there should be a good deal on a Studio. Windows ARM through Parallels is getting pretty close to a dual boot experience.
It all depends on your OS needs. If you want just dual boot with the latest macOS and Windows then Mac Pro 2019 is the ticket.
For me, it is looking like a 6,1 (or two of them for any graphics failure) for 10.13 or 10.14 32-bit apps and a AS Mac of some sort for all the modern apps.