With IBM, one can't help but feel this is a tactic to force layoffs without having to actually do a layoff. I believe they tried similar tactics in their Global Business Services division in the mid-2000s.
If they had layoffs they would have to deal with unemployment payments. They might have to deal with lawsuits. Dpending on laws they might even need to rehire some of them. They will certainly have higher short term expenses than if a bunch of people choose to leave.
If they do get rid of a bunch of people who choose to leave they are also getting rid of people who least wanted to stay, which some might see as a benefit. I don't think this is a good way to decide but I have heard much more stupid logic than this.
I view this move as a life lesson since they will most likely do their best to retain remote workers that are in-line or above when it comes to performance.
The rest will need to figure out what they want to do; you can't cry about this if you did not pull your weight.