I'm not sure about this. Besides the ASUS Z690 Apex getting a revision that is suppose to solve mem OC issues, I haven't heard of others getting it. Also it should be noted that all these OC records are with LN2. Going above 6600 on 4-slot is unlikely to be XMP, plug n play. While it seems DRAM manufactures have 6800-7000 kits ready looking at the QVL, these companies are probably waiting until the next CPU and or chipset.
Yes to an extent. I think they will all support 6400 with a BIOS update. I do not think we will see 6800+ on 4-slot Z690 this generation. When the 13th gen comes out and Z790 (or whatever it is called), it will be easier to tell if it is in fact the 12th CPU IMC or the Z690 MBs that are the limiting factor currently. This is just a guess, though.
Current IMC are not the limiting factor. Most, if not all CPUs run with RAM at 7200+. You have to be really unlucky to get a chip that can't make 7000. The main problem are motherboards because of their design flaws, problems with BIOS, or other things. The most common is ASUS Apex slot issue but other brands have problems with slots too. There are MSI Unify-X that can't boot past 6800 or other models that run at 6400 on one slot and 7200+ on another.
Gigabyte can't even solve DDR5 compatibility issues, releasing 15+ BIOS versions (official or public beta). At least 8 BIOS releases are supposed to fix G.Skill issues and DDR5-5600+ issues, and I still get questions from users if I can help them to make it work on mobos like Z690 Master at 6000+.
We are six months after the premiere, if they couldn't fix DDR5-6000+ issues in this time then they probably won't do that at all (it's not possible or they won't try). I assume that most of the BIOS teams are working on the next-gen mobos already, so most motherboards will get "only" new microcode updates ... and we can already see that. The last 2-3 updates for the most popular motherboards were microcode updates.
Manufacturers have 7000 kits ready for like 5 months but they already changed XMP, voltages etc. You can check what kits were available on various QVL for top OC motherboards and how manufacturers were raising declared max memory frequency for these motherboards. It barely moved since Nov 2021. In the last month, ASUS changed max RAM support for the APEX and Strix ITX from 6400 to 6800. It's related to the new mobos batch and solving the design flaws in the mobos manufactured in the last year.
Not even one kit rated at more than 1.45V from QVL was released in retail. It's because in a specific environment, these kits are losing stability. In the lab environment, all is fine, but it would cause too many RMA on the mass market. This is also why upcoming 6666/6800 kits from G.Skill are rated at CL40/42 and 1.40V while IC could run at tighter timings but not in a PC with limited airflow.