I don't understand this line of thinking. If he didn't love Aston Villa, he'd have left last year, or the year before that, or the year before that. He's entering the peak of his playing career and is tempted to test himself against Europe's best teams on the big stage. If he goes, I will root for him because he's a true Villan, an amazing talent and a very likeable guy.
I'll be pissed off if he leaves and deeply disappointed, but I'll get over it and move on. Villa are back for good, with or without Jack Grealish.