Correct, it would be highly unethical and possibly illegal to require a vaccination that is not approved by the FDA for employment status.
However, full FDA approval will come later this year which will pave the way for companies to require employees to get vaccinated (whether they agree to wear a mask or not). Question is, will COVID be enough of an issue by then for companies to still be motivated to do so. All things, in the United States, point to no. Thankfully, we have the luxury of unlimited Pfizer/Moderna shots which are likely to set us apart long term from other countries using less efficacious vaccines.
Additionally, COVID appears to be endemic in the United States right now from a true epidemiology perspective (the CDC's "you're responsible for your health messaging" along with widespread use of the honor system regarding masks supports this). From a cultural perspective, endemic status is a ways away. Probably not for a year.
Re: WDW, remember, it's Florida. WDW has shown they are already willing to divorce the domestic parks on COVID-19 policies (among other things), due to varying political and cultural ideologies; and they will continue to do so.