And no it's not enough to pull the application, if you've distributed the binary and you've used GPL code you're obligated to release that code.
No, you're not automatically obligated to do any such thing. What happens is that you may be infringing on the copyrights on the GPL'd code, so it's up to the copyright holders to decide what to do: ignore it, negotiate a (presumably non-GPL) license agreement with you, or take you to court. And if the latter, the judge will decide what the punishment should be--most likely it'll be "stop distributing the software and pay the copyright holder $$$$$". It's unlikely that the punishment would be "publish the source code to your app that used GPLed code."
Yes you are obligated to do such a thing, and if you don't comply you can be dragged to court where you could be sentenced to pay for copyright infringement.
3. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:
a) Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
b) Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
c) Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)