I certainly think Steve, more than anyone else, had the potential to bring Elvis round to the understanding and belief that he was able to do so much more with his career. Know he spoke to Elvis a fair bit as far as he was able to while the Special was going on but yes, I would say it was a fair comment that Parker felt threatened by Steve, that he might lose control over Elvis and all that stood for.
He certainly seemed able to bring Elvis down lower than, in Wanda's words, 'whale poop' on so many occasions and it's possible Parker knew some things Elvis wanted exposed such as Vernon's prison record and thus was able to use manipulation and blackmail in his own best interests?
But yes, if things had been allowed to progress on their natural, proper course of action, can see the sky would not have been the limit for the potential that was theirs, don't even want to imagine what the 'Special' would have been like with all those sentimental Christmas songs?! Oh boy!

As it was, an amazing showcase of Elvis' immense talent that was to go down in rock history!
