He did come from a fairly strong-willed family, it's true. That said, I'm not sure why he'd set aside his wife when she brings along a useful dowry (which Fulk OTL insisted on getting back after William's OTL death); it's not like it stops him from having plenty of fun with other ladies of the court (his dad certainly didn't seem overly concerned with marital vows). AIUI, the objections to Matilda's marriage were less about a marriage in principle, than about being ruled by an Angevin (since "obviously" a woman would be governed by her husband); a marriage to Geoffrey's younger sister doesn't have that issue, and does bring some peace and stability to that border.
It could happen, but it would bring a lot of headaches with it. Especially since William Clito (really, the Normans needed to branch out more with their names) is still running around (and OTL made overtures to Fulk of Anjou during the conflict over William Adelin's dowry; a broken betrothal would make that alliance even more logical), and the barons generally being untrustworthy even without the Anarchy to give them an excuse to extort the Crown for lands and titles in exchange for temporary allegiances. That's without even mentioning any plans William Adelin might have in his own right for meddling in France (either in Flanders with its upcoming succession crisis or elsewhere). If he has any sense, he'll stick with the marriage, especially since Henry I (who I'd expect to live at least as long as OTL without the loss of so many of his children in the White Ship and the resultant succession crisis) would live long enough to see the marriage consummated before he died (when Matilda OTL would be in her 20s). We know Henry was very keen on an Angevin marriage to acquire those dower lands and to secure that frontier (both with William Adelin, and then after his death with the Empress Matilda as soon as she became available), so I'd expect him to put his foot down if William Adelin tries to end that marriage.
Ironically, I expect William Adelin will likely be on good terms with his Blois cousins; they were on good terms with Henry I, OTL, despite the looming succession issue.
If Empress Matilda still becomes a widow, she may be packed off to a convent instead of remarrying, if she isn't expected to inherit the throne.