The reason for the delay is unknown. It could be because there just isn't enough supply of chips to justify a new product launch.
Cowcotland reports that Radeon RX 6700 series will feature Navi 22 GPU with up to 40 Compute Units (2560 SPs). Therefore, the RX 6700 XT is believed to offer half of the flagship’s RX 6900 XT Stream Processors. It is also reported that the card will feature 12GB of memory attached to a 192-bit memory bus. The exact specifications of the graphics cards have not yet been confirmed though.Source: VideoCardz
The RX 6700 non-XT is also expected to feature 12GB GDDR6 memory, which might be the reason why NVIDIA is now pushing RTX 3060 with 12GB memory as well, despite releasing an 8GB 3060 Ti model just a month earlier.