Well, for starters, the longitudinal dialectal regions are butterflied away, and it would probably look a lot more as center/expansion pattern.
It's hard to really tell how dialects would appear ITTL and even less their shape, giving our knowledge of late Hispano-Romance is virtually non-existant. We could assume that northern dialects and linguistical ensemble would mostly survive, ut their evolution in Spain would be significantly different. For instance, it's possible that Occitano-Romance might remain stuck in Old Catalonia (although no Arab conquest might mean, depending on the situation, a Frankish partial takeover, so it's not out of the table), and that Galician might not extend south ITTL.
I think a good bet would be a bigger extension of a Spanish language based on southern Hispano-Romance speeches (so a mix between "Mozarabic" dialects and Asturo-Leonese), with an important dialectal differenciation of Pyrenean and Cantabrian speeches, due their important peripheral situation.
Also, the possibilities of Basque surviving improve or worsen?
I'd say improve, giving they're not fighting for regional dominance with Romance polities : I don't think there would be much room for Basque being more used than IOTL, but maybe a more lasting presence in IOTL Navarre and Upper Ebro basin.