No official info is available for the RTX 4000 series, but there have been some leaks. Currently, the only concrete information is its codename: Ada Lovelace.
The Ada Lovelace microarchitecture will be on a 5nm fabrication process, a solid leap from the 8nm Ampere (Samsung) chips. A smaller microarchitecture will result in two significant benefits: more performance for a lot less power.
Thanks to TSMC’s 5nm process, Nivida gets those benefits by cramming more transistors onto the chip.