I'd be perfectly fine with John de Lancie as Q coming back in the new Picard show, exactly the way he looks now. They wouldn't need to try to CGI him up to make him look younger or whatever. Q can look like whatever Q wants to look like. Who is to say, for instance, that Q wouldn't intentionally choose to appear as "an old man" (i.e. de Lancie's current appearance) just to rub it in Picard's face that Picard himself has gotten older? It could be a running thing or it could just be a quick throw away gag at the start to lampshade the fact that John de Lancie is older. I don't care. I just hope that John de Lancie as Q makes some appearances in the new show.