In my opinion, I believe that Core's new owners, Apollo, were approached by EPE/Core in an effort to end the show to save from having bigger financial losses down the road. Remember, the more money that EPE/Core put out the less they made back which affected what developments would get done around Graceland.
Also, the $6 billion dollar City Center, where Viva Elvis is/was held, is said to be a financial disaster itself and isn't bringing in the dollars that they expected. Vegas is still recovering from the recession and the Aria resort is half filled annually that rates have been dropped. Get this, one of the multi-million dollar luxury hotel towers was never completed because of lack of funding that it's now planned for demolition. Talk about flushing money down the toilet.