20 years out means 30-somethings. The Gen-X'ers. There's not as many of them as there are of us Boomers. The age doesn't need to be raised. It's not a mandatory thing anyway. You don't ever have to retire if you don't want to.
As far as taking away benefits from the well heeled, that would be stealing, plain and simple.
Keep it at 67.5. What difference will 2.5 years really make?