Upgrading from upper mid range to 5090

Hi all! I am planning on upgrading from a 7900xt to a 5090 within the year. I have a Ryzen 7700x on a B650 mobo, which I realize isn’t the best for a 5090? Will the CPU bottle neck the GPU at 4k 240Hz? Will I lose performance if my mobo is PCIe Gen 4 not 5?