Sure he gave him a promotion from Grey to White, but it would take more than that for Eru to convince Gandalf to return to human form and live among smelly humans and hobbits once more. So what else did Eru offer Gandalf to persuade him to become an old man again?
His love of the halfling's leaf would've sent him running back to Middle Earth with or without the promotion! That, and the chance to stick it to Saruman!
