Yes but now there is no incentive to make a patch. They don't get paid more to make free patches. Unless you make it a monetary incentive for them to make a patch they will put little to no resources into doing it.
They never did fix the original FO3 game breaking bugs. They figure once they got your money they are done. To this day I can't finish the FO3 main quest because the "waters of life" part of the main quest freezes every single time. I can do other things just not the main game. I wonder when that patch is comming? My guess is never.
Strange, I played an unpatched FO3 (the original disc, used, not the GOTY edition) and completed the main quest twice and two DLCs. You're right that patch isn't coming because they've moved on, and clearly it's also something that's not effecting as many people as this DLC one is apparently.
Anyway, they've said they're working on it, the NV patch to fix the DLC is coming. It may not fix all the quest bugs, maybe certain quests will be broken forever (depending on the path you take), but it'll fix the DLC issue and the freezing getting into Vegas, the two big ones. If you're skeptical... then sure, go return the game. But it's not going to hurry things up.