Yes there will always be buyers, but for what price?
If someone places a humongous market sell order then it will rip down the bid order book to a very low price, which will (if it's low enough, i.e. china dumps) dissolve confidence in other holders causing a selloff avalanche and the order book will collapse leaving only the US to buy them back using physical assets or more likely screw the whole deal (which could lead to war).
This is not "conspiracy theory", this is a fact of free markets. The holders all know the position they are in, they understand what a bond is perfectly, they are no longer in it for financial gain, the big holders use it as geopolitical leverage tool and will make a sacrificial move to crush the USD if they feel overly threatened.
There are two end solutions
[1]
The books are balanced which is highly unlikely considering the US debt is growing exponentially and not shrinking.
[2]
War, a fair assumption considering USA has used much of it's petrodollar profits to build quite a formidable military.
It still looks like a conspiracy theory. No rational entity would dump by placing a "humongous market sell order". And even if that happens, this dumb entity will just give some free arbitrage money to the most important Treasuty bonds traders - primary dealers. If the current institutional structure of the U.S. monetary system is concerned, the rates of treasury bonds are simply a product of federal funds rate expectations over the bond's maturity. And this is what this "free market" is doing - trading these interest rate expectations. If fed funds rates remain the same, bond yields will converge back to where they were before the selloff.
So, the most likely outcome is
[3]
Things continue as usual.