Yes, most certainly they can do that BUT, what they have done is UNconstitutional. Period.
An agreement between 14 senators is NOT binding on the President. You can not amend the constitution this way.
But the democrats will act AS IF this is now what "advise and consent" means. Do you really think that the democrats won't do this? When has it ever meant that the President MUST talk and get their approval first for his nominees?
Well Linsey Graham and Saxby Chamblis tried to sue to have the Courts declare judicial filibusters unconstitutional. I don't think they won.