The line wouldn't get cancelled while there are plenty of people missing 2 of the turtles. Lines die after the public's thirst for the major characters is quenched -- not before.
The question is: how many were made? How many people are still willing to buy them? If the number is large, then wave 2 could be looked at as really being the first wave of the line -- considering how the real first wave was handled.
This isn't a typical turtle line, best I can tell.. Typical turtle lines probably had a gazillion figures. In this case, you are dealing with a handful of figures.