CyanogenMod 12.1 is not here yet, but you can get an unofficial build for the Galaxy S5 now. This will bring some Android 5.1 action to your device. This is an Alpha build so you can expect some bugs. You will need to be sure to install the 5.1 Gapps or you will be without the Play Store.
So far the whats working list includes:
wifi
data
bt buggy
gps
cellular service
camera
mms
Mods
Their is nothing listed in the not working section, but im sure there are a few things here and there that will need to be fixed in later builds. Custom mods include bootanimation, wallpapers, wallpaper app, switch for su notification in status bar, home screen rotation, audio mods, save picture to sdcard option, and the tn tweaks section. Grab this rom for your device below.
via XDA