No. According to a copy of his death certificate, Walt Disney died of lung cancer and was creamated at Forest Lawn Cemetary on 12/17/66 (two days after he died).
The rumors probably started since the grounds keepers at the cemetery won’t disclose the location of Disney’s remains.
Evidently, Mr Disney spend a lot of time under the Pirates of the Carribean section of Disneyland. The rumor is that Disney was cryogenically frozen and was tucked away nicely under the Pirates exhivbit. As the story goes, Disney wanted to be frozen in time and unfrozen after there was a cure for cancer.
That however didn’t actually happen.