For those of you with T-Mobile or Canadian Galaxy S5, you can get Lollipoppin today not when T-Mobile or your carrier decides to upgrade your device.
You can get it through the VisionX ROM by XDA user AxAtAx. This is a stock Android 5.0 Lollipop ROM with root that you can install on SM-G900F/900M/900I and also the T-Mobile SM-G900T and Canadian SM-G900W8. Yes, this is actually based on SM-G900F so you will lose WiFi calling but no carrier-branded bloatware.
Compared to 100% stock firmware, this ROM is way faster and has absolutely, and also ships with KTweaker kernel, which allow you to get up to 3Ghz overclocking (I recommend up to 2.764Ghz unless you live in Alaska) and super-zippy TouchWiz launcher.
Overall, this is probably the best way to ugprade your S5 to latest TouchWiz lollipop for pure stock rooted experience without all the bloatware/crapware. So, if you have an S5 model that supports it, try it out and do let me know what you think!
Download Stock Android 5.0 Lollipop ROM + Root (For SM-G900F/900M/900I, T-Mobile SM-G900T, and Canadian SM-G900W8)
To install, reboot into recovery, make backup ROM, wipe data/factory reset, install ROM, and reboot. (If for some reason you end up in a bootloop or get force-closed keyboard error on boot, reboot into CWM recovery, go to Mounts & Storage->format /system. For TWRP, go to Wipe->Advanced Wipe->Wipe /system.)