So, a deal has been reached on the Senate filibuster issue. For now.
I'd like to offer an open-ended prediction: Any legislative action which requires a 2/3 majority, but which can have that requirement changed by an action that itself requires only a simple majority, will inevitably be changed, sooner or later, to require only a simple majority.
Why? Because sooner or later, the majority party will find itself in a situation like the one the Republicans were in here: They have a simple majority, but not a 2/3 majority. They don't have enough votes to implement an action requiring a 2/3 majority, but they do have enough votes to change the requirement such that the number of votes they have will then be enough. In other words, they have enough votes to do what they want to do, they just have to go through the extra step of changing the rules first.
In a game-design sense, the Senate rules are broken: A 2/3-majority-requirement that can be changed by a simple majority collapses to a simple-majority-requirement.
It's easily fixed: Just pass a new rule that any stated majority requirement cannot be changed by a majority vote of less than the stated requirement being changed. That is, if an action requires a 2/3 majority to pass, then the rule requiring it cannot be changed by less than a 2/3 majority either.
Otherwise, I guarantee something like this will come up again.