Until an ability score bonus—no matter the bonus's source—has been in place for 24 hours, the bonus is only a Temporary Bonus, and the bonus has a more limited effect than a permanent bonus. For example, a temporary bonus to Wisdom "gives you a bonus on Wisdom-based skill checks and Will saving throws[, and t]his bonus also applies to any spell DCs based on Wisdom." As its unmentioned as a feature of a temporary bonus, creature's spellcasting is unaffected by a temporary bonus.
After the ability score bonus has been in place for 24 hours, the bonus becomes a Permanent Bonus, and it's as though the creature's ability score had actually increased. Because a permanent bonus "[m]odif[ies] all skills and statistics related to that ability [and t]his might cause you to gain skill points, hit points, and other bonuses," the game recommends that such permanent bonuses "be noted separately in case they are removed." Like, y'know, when you decide to use again the special ability change shape. A creature's spellcasting is affected by a permanent bonus.
For example, Abe, a coldborn skinwalker cleric 7 that normally possesses Str 14, Dex 8, Con 18, Int 10, Wis 16, Cha 10 prepares his spells using his Wis 16 while in his normal form. Later that day, he uses the ability change shape to assume semiursine form, increasing his Wis to 18. Except for his spell's saving throw DCs, Abe's spellcasting is unaffected by this temporary bonus.
Abe decides to remain in his changed form for 24 hours. When he next prepares spells, he'll prepare spells as if his Wisdom were 18 because sufficient time has passed to turn the temporary bonus into a permanent bonus.
After having prepared spells in his changed form, Abe returns to his normal form, dropping his Wisdom back to 16. He keeps and is able to cast his prepared spells, but their efficacy is slightly reduced by his normal form's lower Wisdom.
That same day, Abe uses the ability change shape again to assume semiursine form again, restoring his Wisdom to 18. This is now again a temporary bonus, and it'll be 24 hours before Abe can prepare spells again using this higher Wisdom score.