The toothpaste will be out of the tube. Any future Democrat majority will be able to pass any budget they like. Remember how much Obamacare was "debated" before finally passing? Remember all those back-room deals that happened? Forget all of that--simple majority, Dems pass whatever they like.
Not a single republican voted for Obama care and they literally cheated the process to get it passed. They would have removed the filibuster at that time if they had to.
There was no back room deal to avoid a filibuster back then; they just found a different way to cheat the senate vote.
Remember it was the democrats who removed the filibuster for judges, the toothpaste is already out of the tube, they will do it again anytime they need to regardless of what republicans do now.