Previously, the Fedora kernel package would call a script called 'new-kernel-pkg' to do the boot loader configuration addition, initramfs creation, and depmod steps in the RPM %posttrans script. That script is provided by the grubby package, which despite its name doesn't mean it only works with grub. It works with grub, grub2, silo, yaboot, lilo, and a variety of other bootloaders. However, to the best of my knowledge, it is a Fedora specific package. The other distributions all use their own flavor of initramfs/bootloader tooling for one reason or another.
The kernel-install tool provided by systemd is aiming to replace all of those tools. It was created in part to support the Boot Loader Spec, which aims to create a cross-distro way of managing boot loaders and boot loader entries. The intention is to make dual/multi-distro booting work well without requiring a lot of manual hacks or configuration. If you have questions on this, I would encourage you to talk to Harald Hoyer or Kay Sievers as they're driving that work.
At the moment, Fedora's kernel-install is patched to still call new-kernel-pkg if it exists. That should easy the transition for existing installs and result in machines still working. About the only fallout should be that you won't be able to install Rawhide kernels on older releases of Fedora. The RPM requirements specify that you have systemd >= 203 and dracut >= 027. Of course, there still may be bugs. If you're running Rawhide and hitting issues when you install or remove kernels, let us know.