The Alder Lake-S product launch will not take place at the same time as the Intel Innovation event (October 27th). At the same time, Intel will launch its first high-end Z690 chipset for the next-generation CPUs. This will be the first chipset from the 600 series, with others (B660, H670) rumored to debut early next year. The Z690 motherboards will feature an LGA1700 socket, only compatible with Alder Lake-S CPUs and more than likely its successor, Raptor Lake. The motherboards equipped with the Z690 chipset will also support DDR5 memory technology, but models with DDR4 support are also planned.
BTW, the EU price for 12th Gen Alder Lake-S has leaked online, you can take a look here.