It is no more difficult to fork a PoW than a PoS, all depends on if the users upgrade or not.
Incorrect disingenuous fool who is on a trolling tirade and destroying his reputation for everyone to see:
I don't agree with smooth's claim that the mining nodes can't fork the block chain without the support of the users who transact; because users need to be on the longest chain else double-spends on the competing forks will force payees to recognize only the longest chain.