I don't think it has more PCIe lanes -- those are limited by the IO die, afaik.
As DDR5 is coming out next year, that will mean a new socket, limiting the upgrade path for the CPU, RAM & Motherboard. Although, 16 cores ~4.5ghz shouldn't be a problem for the near future (maybe 5 years even). Same goes with the PCIe bandwidth.
Edit: Just done some checking, I appears the 3950X has 24 PCIe lanes (16+4+4), but they are twice as fast, so not far behind the current 2nd generation ThreadRipper!
The chipset multiplexes up to x16 lanes of "stuff" onto the x4 chipset lanes from the CPU.
All of this is physically determined by the pinout of the socket and none of this can change unless AMD moves to a new socket. What did change is the speed of the lanes - x4 lanes on 4.0 is twice as fast as x4 lanes on 3.0.
AMD, like Intel, likes to pretend that chipset lanes "count" as full CPU lanes, arriving at a total of 36 effective lanes. But that's nothing new either.