Islamic victory at Tours would have done the trick, paving the way for an Islamic controlled territory in Western Europe, plus they would be within striking range of Britain if they had conquered France..
No. For three reasons.
1)They didn't had enough men. In 750, it's estimated you had maybe 5 000 Arabs and 15 000 Berbers for the whole Spain (with 3.5 Millions of Hispano-Romans incunding Germano-Romans) with Arabo-Berbers from Ifryqia and critically Maghrib joining for some times before returning in Africa.
Gaul had around 10 Millions of inhabitants (with 3/5 north of Loire admittedly, that put the southern population around 4 millions).
And for raiding Gaul, you certainly can't put the WHOLE muslim army out of Spain, 10 000 is the best you can gather.
Even for what they held in Gaul (roughly Septimania) they didn't managed to have more than one town garrisoned (Narbona/Arbûna) with the whole country being under the hands of the Occitano-Roman nobility -mostly from visigothic origin.
2)Tactics.
The usual tactic is first raids to have plunder that happen to allow explore the land. If all things are okay, then they tought about attacking.
They did twice, not only for raiding (as they did in Sens or Tours) but for conquest against Aquitains in 721 and in provence around 735. They failed, big time.
Partially because Franks used foot-based tactics (it's possible, while not prooved, that Charles Martel reused some roman formations) with heavy infantery that was quite useful against light cavalry. Not only that tought, the Aquitains relied much on the light Gascon cavalry.
You have too the terrain : it's one thing to fight in land as southern Spain and Western Africa, it's another to fight in more cold, more foresty, etc.
It's maybe one of the things that explain why they were sucessful for raids in Provence and up to Sens and not towards the Aquitain way.
Then, the Gaul wasn't the Visigothic kingdom plagued by civil war. Aquitaine was quite of a stabilized territory, and Charles Martel reunified a Frankish Kingdom that was only briefly in civil war (his father Pépin II managed to unite it since the end of VII century).
3)Context
The Arabo-Berbers knew that, and if they didn't forgot all hope to take over Franjs, they had more cautious and realist objectives.
Wanting to take revenge on the defeat at Tolosa (often considered as more important than the one at Poitiers for the Arab scholars of MA) they decided to plunder the most rich, most important site in Gaul : St Martin's Basilica.
Almanzor didn't tought a different way when he plundered Compostella : "there's good loot and it would teach them".
A victory at Poitiers is possible, tough would need a POD that could butterfly the expedition. It would end as a raid though, and Arabs would come back with more wealth than OTL.
There's no way it would be enough to butterfly the Berber Revolt of 740 and the subsequent civil wars in Al-Andalus, nor the Abassid Coup. With these events, Al-Andalus wouldn't be in position of attack and invade : good enough if they keep what they had.