First of all, the Kor'kron in vanilla was indeed Orc only and served as the elite guards of Thrall. Later their numbers seemed to rise, included other races as well and were assigned multiple tasks. So you see, they aren't an Orc only organization as you say they are. Perhaps the elite guards of the Warchief are though.
Second, you seem to blame Garrosh for the lock down of Undercity while it was in fact Thrall that ordered it.
Third, the Kor'kron didn't betray the rest of the Horde, the rest of the Horde betrayed the Orcs. Garrosh had a problem with Vol'jin, since he was an insubordinate. The Darkspear helped their leader and thus were also put under watch. However, outside of that it is Lor'themar and Baine that choose to start a war with the Orcs, not the other way around. So you see, it's the rebels that betray the Orcs, not the other way around.
For the record, seems like many people like to bring up WWII when comparing this situation, but it was France and the UK that declared war on Germany and not the other way around as many seem to believe.
Anyway, why does the Horde need a new elite? I think the Kor'kron functioned just fine under Thrall. They are simply 100% loyal to their Warchief, so whatever order they're given they follow it. They don't care if it's Thrall or Garrosh that gives the order, whoever the Warchief is they will listen to. There is no need to get rid of the faction. I think Saurfang retaking control would be the most fitting, and they should remain the Orcs' as well as the Warchief's elite soldiers.
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Originally Posted by Combooticus
Did the Praetorian guard cease to exist after Caligula? or Nero? Nope
They will survive MoP and will have to be reorganised but the name will still stand imo
They are a tool of the Warchief Proud and Loyal and will do what ever the Warchief says thats there job.
If the Warchief says you will give out fluffy bunnies to orphans on childrens week the Kor'Kron will do it.
If the Warchief says liquidized some rebel trolls the Kor'Kron will do it.
Yeah, exactly. No need to blame them for the orders they were given.