The genuine "official" date on which they will "START" pushing ICS to the Iconia A500 is last stated to be 4/27. Hopefully we'll start seeing some action then on getting the update.
I don't know if this will matter in your plans to create an automatically updating utility, but it seems ICS has "abandoned" some longstanding file transfer abilities, most notably being able to connect by USB as a "Mass Storage" device. In so doing, they are seeking to limit which files can actually be copied. I ran afoul of this issue in 2 different ICS ROMs which interfered with my weekly routine of backing up both Internal Storage and External SD. I know there is a project underway here on XDA to restore Mass Storage access to ICS on some phones, but it did not work for me on the A500. Hopefully it won't prevent what you would need to do to keep things updated for the GPS Fix.