Aquitaine was completly lost to the Franks since 719, as Hilperic recongized Odon as king. In fact, the fall of Tolosa could even be used by franks to regain the 1/3 north of Aquitaine and its rich monasteries and lands.
For the rallying, it's to be forgoten : Charles of Heristal have serious problem with Hugonids and Bavarians at this time. Aquitaine is considered as a foreign country and if he can hold the 1/3 north and Provence, it wouldn't be amazing to see a stalemate.
On the ummayad side, however, it would be likely as Septimania, with only Narbona and Tolosa (maybe Bordeu or even Ausa if they can) actually occupied by arabo-berber leaders with all the country side by gothic/aquitano-gothic (in septimania and Tolzan) or aquitain/vascon in western part. Because of the lack of men, arabo-berbers would be likely unable to settleing Aquitaine, not by leaving many hispanic regions to independent christians, ironically giving even more chance to the Kingdom of Asturias to appear.
A large part of OTL Gascony would likely espace islamic authority, as Asturias and pyrenean counties.
But, after the Berber Revolt of 740 (i don't see a victory in 721 butterflying this), it's likely that aquitain noblilty would regain more and more control of the land, eventually taking Aquitaine/Septimania for themselves, or (but more unlikely) submitting to the franks in exchange of autonomy : not a independen big state as the one of Lop and Odon, but a fragmented region.
