I killed a zombie pigman about 54 days ago in game, and died hundreds of times trying to get my stuff back, but every time I killed all the pigmen, more would spawn, all still hostile. it got to the point that when I would walk through the portal, I would lag from the LITERALLY HUNDREDS of pigmen that were surrounding the portal, and die before I could take a step. fast forward to today. I go into the nether with all my gear, planning of farming some ghasts, and the pigmen are still there. I ran thousands of blocks from the portal, came back a long time later, and they are still hostile. this is absurd.
Try to stay in the Nether, protected from Pigmen, for about 15 min.
Pigmen now have a Timer after they were made hostile, which maximum is 13min and 20sec.
More info can be found here : https://www.youtube.com/watch?v=e6dgAckaElM
But Pigmen spawning miles away from the angry ones already aggressive still may be an issue.