That's still not a straightforward question to answer, because transistor shrinks aren't just about shrinking some dimensions while others stay at their limits. Transistor geometry has changed in more fundamental ways. Beyond ~28nm, the industry switched from planar transistors to FinFETs, so now instead of gate width we have an extra dimension and have to consider stuff like fin height and fin thickness and pitch. Starting around 3nm, we'll be seeing "gate all around" transistors—GAA FETs, in the form of nanowire, nanoribbon or nanosheets.