If the frame rate of an animation is remapped, how can the IPO curve be updated to reflect the new length.
You mean remapped as in “MapOld/MapNew”? I would think that it needs the existing IPO as the (old) variable to map the New against; if you change it then you change its product too.
If you mean you change the number of frames as in the length of the annimation then you can scale the IPO’s constrained to X with MMB.
Same if you mean changing the framerate.