Lol lollipop ain't that bad. If samsung leaves the 5.0 update for s4 it's however their chose sure it wasn't that good and missed much that they promised trey rolled out a half baked promise.
It's one way good in other way bad.
S4 will get latest android 5.1 when it's currently latest.
And not stop at 5.0
Bad thing is that 5.0 mostly affected nexus devices in those claims. Not any other devices.
Most thing that was bad was that stock apps were outdated and not materialized sure there was flaws and bugs for their devices as well but this leak doesn't have much flaws.
The more you work on it and fix these issues it will be good
However I wouldn't be surprised if samsung did this.
Remember 4.3 they skipped it when it was almost done.
Just wait for a known source to claim if it's true or not.