Rumor is true or false Rio will not be hosting the event ?
False ... there are no changes to date.
There have been rumors about this almost every year. As of right now, there isn't another convention space large enough at any Caeasar's Entertainment property. The company is building a large convention space behind Harrah's and the Linq Casino (formerly Imperial Palace). It's possible that the new space will be large enough to host the WSOP. If that is the case, then when that space opens, they might consider moving the WSOP over there. While that wouldn't surprise me, it's still way too early to know whether or not that will happen.
I'd bet real money the Rio doesn't host the 2020 WSOP. The convention center Dave mentioned is scheduled to be at least partially ready by next spring, just in time for the World Series. Just look at what CET has done to the Rio, or rather, what they haven't done- it's been under deferred maintenance for years now, and soon the Rio's rooms will be the only Vegas hotel rooms that the company hasn't updated. The property is also actively being shopped, with at least 2 serious inquiries. It really is the outlier among their Vegas properties. Not only will the 2020 WSOP not be at the Rio next year, Caesars Entertainment won't own it. Bank on it.