The 2.5 months was plucked from the speculation tree
But also with the rumour of the R350 announced to compete with the NV30. The R300 is, what, one month old now? If the NV30 is announced mid November and so is the R350 then that will be roughly 2.5 months.
Even though the card isn't released you are effectively saying the previous model is now out of date and requires a refresh.
You are probably correct with your assumption about ATis .13u progress, after all it would make sense. They are probably having ten kinds of hell with the process, it's just that they have a card to cover thier asses in the meantime.