I don't think Pac-Man was the deciding factor or anything. He really is the best and most obvious choice as far as Namco characters go. I was never really clear on how much, if any, of Xenosaga's rights were held by Monolith Soft (Bandai Namco released some Xenosaga figure sets after the sale, but the games have yet to be re-released digitally or as an HD bundle) so depending on who owns what, KOS-MOS could be a first party character on a weird technicality. I always figured her chances begin and end with Monolith Soft regardless of who actually owns the rights to Xenosaga and even then, I never thought she was a realistic choice, just a cool one. It would have been nice to honor (arguably) Tetsua Takeshi's most popular creation, but Shulk is just a better choice at this point. Xenoblade is more relevant and 100% owned by Nintendo.
As for serious predictions for this upcoming announcement, I can't really argue with Shulk, but I'm still going with Bayonetta. Ride that hype train all the way to October.