First, if Apple declared, right now, that full remote was an option, what you say is
still true. i.e., in two years, management could decide to take away that benefit.
So I don't see how that kind of reasoning is useful when making an employment decision today. Getting up in arms about a purported future two years from now is just not rational, and is ultimately a byproduct of fear.
More broadly, this has always been true. Employers have always been in an position where they could change the terms of employment, and employees have always been in the position of being able to make a choice as to whether they would be willing to accept those changes. The WFH situation isn't special in that regard.
Second, this could go either way. Future leadership could equally decide Apple will go full remote. But the assumption is always that future change will take away the benefit rather than expanding it. That the slippery slope will always be to the worker's detriment. That's just another form of management distrust.
Edit: And oddly, given the current demand for positions in technology companies, that distrust is especially unfounded. Employees have never been more empowered. The sheer demand for labour means that any company instituting a policy that's broadly unpopular will lose staff. Absent a profound change in the labour market, in that context it would be insane for Apple to communicate a hybrid work policy, now, only to renege on it.