It's not a deal breaker for me either way.
I would prefer that they recast the role. If they reflect the 10+ years that have passed between movies, it would easy enough to cast a "grown up version" of Shia's teenage Mutt.
And in reflecting the 10+ years, I would hope that they allow the character to mature emotionally as well.
Be kind of sad if he was still a jittery greaser wannabe when it's the late 60's and he's pushing 30.