It's based on expansion. Currently auto grants up to CoTF. So basically level 100. You will still get a few past 100 but I think that was the ones that have a cost of zero anyway but I could be wrong on that part. Some also never auto grant like the tradeskill ones.
To expand on the above, the AAs which are auto-granted are a set number of expansions behind the current one. So when the next expansion comes out the AAs from TDS will be auto-granted. This only applies to AAs which you must purchase with AA points. Those AAs which are granted via quests, missions, or raids must still be earned those ways.
