Not only is this simply untrue, but even if it were it would not afford Disney anything they would consider to be worth the investment of moving Small World.
Festival of the Lion King is a Stage Show, and as far as the infrastructure of Disney stage shows go, it's a fairly traditional one. There are no crazy lifts in the stage, no unusual engineering to the theater -- every component of that show is designed to have been loaded in when they needed to and taken out when it's time to remove the show. The scenic elements are on wheels; many of them are old Parade floats, literally designed to be moved from place to place.
It's a Small World was and is not similarly designed - it is a huge animatronic production filled with heavy machinery and large, bolted-down set pieces in a purpose-built building that was designed to be flooded and be as permanent as can be until they decide to demolish it at great expense or close the park and let the ride rot with it.
The new theater for Festival of the Lion King was designed with this particular show in mind, but a Theater is by it's nature a flexible space, and you better believe they designed it in the understanding that they may one way wish to put another show in there. Small World was designed to last until the building fails or until the end of time, whichever comes first. In Tokyo, it seems, the former is winning that race.
BUT, even IF Disney moved Festival of the Lion King, think about what they got out of it. For the several millions they spent building the new Theater, they got a space in their theme park ready to handle this and whatever the next show one day is, but also the chance to expand their fledgling park in the best possible way, with a visible franchise taking up that newly available prime real estate so that the overall park can more efficiently make back the money that has been invested in it.
Magic Kingdom has no such issues. Beyond the park having plenty of more accessible real estate for them to build upon, Magic Kingdom is making BANK. There is NO financial incentive to undertake worth that exhaustive, and no creative reason either. If they're willing to shoehorn Frozen into Norway, then no idea they have is in their mind *so perfect* for that spot that they wouldn't dream of finding another place to build it before tearing down one of their most enduring and endearing classic attractions and putting it there.
The cost then, further that the demolition costs, to rebuild Small World somewhere else would be SO much higher than building a new theater for FOLK that it's not even funny. Tokyo is making this investment solely because the alternative is to let the attraction fail, and they are thankfully unwilling to do so. If they could keep their Small World running in it's current location until the end of days they would be more than thrilled to do so. The fact is, they can't, so they're taking advantage of the situation.
TL;DR - It ain't happenin'. Ever.
