Q. Will openSUSE Leap work with newer computers?
Yes - openSUSE Leap 15.1, shipped with version 4.12 of the Linux Kernel, which provides very modern hardware support and graphics drivers were backported from the 4.19 Linux Kernel.
Q. Is the Linux kernel/GNOME/KDE/something else older than the version in 15.0?
Kind of - openSUSE Leap 15.1 contains Kernel 4.12, GNOME 3.26 and KDE Plasma 5.12. Same versions as in Leap 15, but Frameworks is newer.
Q. Will openSUSE Leap work with older computers?
Maybe - openSUSE Leap will be built for 64-bit architectures only, and hence will not run on older hardware without 64-bit support.
Q. Why does it have such an old kernel?
See here for the explanation: Why is the kernel used by Leap so old?