It turns out that Intel’s Z490 motherboards will indeed support the 11th Gen Rocket Lake-S processors in-addition to the PCIe 4.0 standard (across 20 lanes). This was confirmed by Gigabyte in an video detailing the company’s Z490 boards for the 10th Gen Comet Lake-S desktop parts.
Earlier leaks about the top-end 400 series motherboard had indicated that the next-gen Rocket Lake chips might retain the LGA1200 socket along with the Z490 chipsets. There have also been claims that the new motherboard will be “hardware-ready” for the newer PCIe 4.0. The recent Comet Lake-S and the high-end 400 series chipset launch seems to confirm it with most OEMs mentioning it as a feature of their flagship boards.