I can't see him trusting Harry enough to make a final choice to pass it on to him, at this point.
I think it's pretty possible Eb will 'see the light' in BG - quite possibly while dying. Harry's apparent "death" in PT might have been enough of a shock to make him reconsider, anyway.
But if an excommunicated member had possession of the blackstaff, they're eminently capable of just killing him to recover it.
In general, yeah.
But there might be two issues in this case.
- If the Blackstaff is Mother Winter's walking stick (as seems likely) the Council killing the Winter Knight to recover it might be politically risky. Winter probably has a better right to it than the Council.
- Harry is Warden of Demonreach. It would be one thing to assassinate him, quite another to publicly announce that he was expelled from the Council and *then* come after him, since he could take refuge on Demonreach. Their best bet would be to take someone Harry cares about hostage... but after the Red Court, that might not feel very safe.