Yeah, it's not exactly a surprise these are in the pipeline, and neither that they are now listed on the Eurasian Economic Commission (EEC). In this round, it's ASRock who registered a Radeon RX 6600 XT and RX 6600. (updated)

It looks that AMD, in the upcoming months, is to introduce the Radeon RX series 6600. Asrock has registered internal SKU numbers. The cards likely will get 8 GB of memory as standard. But the specifics here are, of course, guesswork, 128-bit; however, it seems feasible if some L3 cache is applied.

ASRock has registered the following cards on April the 27th:  ASRock RX6600XT PGD 8GO, RX6600XT CLP 8GO, RX6600XT CLD 8GO, RX6600XT CLI 8G, RX6600 CLD 8GO, RX6600 CLI 8G.

Update: up to 2048 Shader cores and 8GB:

Newly leaked information has surfaced the mighty web. Rumors originating from Chiphell now indicate the AMD Radeon RX 6600 XT would feature a Navi 23 GPU with 2048 Shading processors. XT variant would have a fully activated GPU. The Radeon RX 6600 non-XT allegedly is going for 1792 shading cores. The secondary rumor is indeed 8GB at a 128-bit wide memory bus. (via Chiphell via @9550pro via Videocardz).

Update:  things are moving much faster now. The two cards have made an appearance in GPU-Z at the aforementioned specs. RX 6700 XT at 2048 shading processors, 128 TMUs, 32 ROPs, and a 128-bit wide GDDR6 memory interface with 8 GB of memory. The RX 6600 (non-XT)listing 1792 shading processors, 112 TMUs, 32 ROPs, and the same 8 GB of GDDR6 memory. Both chips feature PCI-Express Gen 4 support. Navi 23 uses only 8 PCIe lanes though, interesting; raytracing seems to be there as well. Check the thumbnails via ChipHell Forums

AMD Radeon RX 6600 and RX 6600 XT Show up in GPU-Z Screenshots