I've been looking a bit around concerning the GL1. I'm pretty convinced now that these units won't receive an official update from TomTom. The GL1/Hammerhead chip was launched sometime around 2004. The most prominent device using this chip is probably the opensource linux-based OpenMoko Neo1973 smartphone. Due to their stance towards promoting opensource and openhardware, they were not happy that the A-GPS chip came with a closed-source binary blob "gllin". There were quite some efforts reverse engineering the binary and to create an opensource interface, however unsuccessful, and with the release of the newer OpenMoko Neo FreeRunner, which uses a different GPS chip, there wasn't much interest in pursuing further reverse engineering.
This binary-to-NMEA-converter "gllin" is probably what is "gltt" on our TomToms. Now it seems this is not so closed-source, but possibly handed to TomTom under an NDA. I believe this because TomTom was able to make adjustments, e.g. they hard-coded the file name of the output fifo to be "/var/run/gpspipe", while it is different in "gllin". Anyway, it's a closed-source blob and probably even if TomTom wanted, they can't release the source, as was requested by someone on their forum.
This brings me to the conclusion as to why TomTom won't fix GL1 devices: GL2 "Barracuda" is - as the name unambiguously suggests - the successor (launched in 2007/2008 still by Global Locate) to GL1 "Hammerhead" (note how they seemed to like fish :en:). I guess both blobs "glgps" and "gltt" aren't too different. If TT was able to fix the bug in "glgps", it shouldn't be much more difficult to fix "gltt". Or maybe they don't have access to the source anymore (contractual agreement)? In that case, I don't see why Broadcom would submit a patch for "glgps" but hold back on "gltt", if it was available. So, unless Broadcom decides to publish the source for the translator, I don't think we can expect an official update for GL1 devices!