First, I read this CSM article, which quotes Professor Chemerinsky, saying I'm not sure what - that filibusters are sometimes good, and not unconstitutional, but the Senate can change its rules, which is not really what I expected from him.
Then, I googled "Chemerinsky" and "filibuster" and discovered this article by Professor Chemerinsky, which seems to say the same thing, that filibusters are sometimes good (and sometimes bad) and not unconstitutional, but that the Senate can change the rules:
"Our conclusion is that supermajority voting rules in Congress are not inherently unconstitutional. Neither the Constitution's text nor an underlying philosophy of majoritarianism impose a general rule that a majority vote must be sufficient in all instances. However, it is unconstitutional for Congress to bind future sessions of Congress. It is a clearly established principle of constitutional law, supported by fundamental democratic principles, that one Congress cannot tie the hands of future Congresses."
Next, I see this Professor Bainbridge post, which cites the 1997 article, but also that Professor Chemerinsky has been going around saying that retaining the filibuster is a good idea.
Next, I see this ACS post, which is no different.
So, my guess is that the Democrats would change the rules the first chance they get, and Professor Chemerinsky (and friends) would say it's not only legal (as he has already concluded) but also it's not so undemocratic as if the Republicans had done it, because the Democrat states are bigger than the Republican states (or whatever his lame point is, and it is lame, the whole idea of the Senate is anti-majoritarian in favor of small states). By then, perhaps, the Republicans appointed to the Supreme Court by President George W. Bush will be very old. (Professor Bainbridge, evidently, fears that such a day will come much sooner than he would like.)