Incredible. First of all, we know that won't happen. Second of all, that is NOT what Article V says. "Two thirds of the several states shall call a Convention for proposing Amendments" is in black-and white in Article V for the very reason that the framers knew Congress might not cooperate in passing wanted amendments. Schlafly needs to do his homework.
Article. V.
The Congress,
whenever two thirds of both Houses shall deem it necessary,
shall propose Amendments to this Constitution,
or,
on the Application of the Legislatures
of two thirds of the several States,
shall call a Convention for proposing Amendments...
If you ignore the words between the commas, Article V does reasonably reduce to "The Congress, ... , ... , ... , shall call ... ," imo.
However, Article V's "Congress shall call " doesn't give Congress a choice any more than the 1st Amendment's, "Congress shall make no law ...," does imo.