I have no idea what industry you are in but I suspect you are lumped in with "about to retire anyway" people. You are expected to be a good little plow horse and dutifully do your job for a couple more years to let your new (much younger) bosses come up to speed. Excuse my blutness but I suspect you are considered expendable. I suspect that they didn't talk to you about getting your boss' job because they never thought about you getting it or wanting it.
Of course, I'm 60 and my company considers me essential to their operations.
Actually, I used to have an "important, senior management postion" in a large international company; but in a company reorg about 10 years ago, I was informed as to how important I really was. Fortunately, I just happen to have the right degree and the vestiges of a scarce skill set so I can get billed out to unsuspecting clients. I'm FI and I don't care if they run me off. The w*rk is easy and I can't spend all the money they give me. If this job wasn't so easy and flexible, I'm sure I would have retired long ago. God save me from anything resembling my past life.