No, Red Hat is not going closed source. The GPL only stipulates that you have to make source accessible to licensees and the licencees of RHEL are Red Hat’s paying customers. Red Hat has already stated that RHEL subscribers keep access to the sources via Red Hat Customer Portal.

According to AlmaLinux, there seems to be some licensing on Red Hat Customer Portal that seems to block republishing sources acquired from it. I wonder if that doesn’t run afoul of the GPL. It is an additional restriction on the source code, which terminates the GPLv2 automatically. Would be an interesting situation if Red Hat loses access to the Linux Kernel over this.