" the night elf Sentinel Velinde Starsong was given the task of clearing Felwood of demons. She prayed to Elune and was granted a magical scythe which could summon worgen. Using the Scythe of Elune, she summoned a very large number of the creatures to fight at her side against the demons. Later Velinde began to notice that some of her force were unaccounted for. It was as though the Scythe of Elune no longer required her presence to perform the summoning process."
It can be assumed that Aragul summoned the worgan that were already here...but I find it much more interesting, that we were sent back in time via CoT, in order to help clear felwood disquised as Worgen and thats why they were "unaccounted" for at the end...we simply went back to our own time, and maybe perhaps we will find out where the Scyth of Elune truely is.
I know the scyth will be found in Gilneas, I don't know if it is explained how it got there or not.