You know, if this is really true (and I still don't believe he'd do such a thing) but he is the one who is acting in a hurtful way.
It truly is unprofessional to announce you are not coming to a con without even telling the organizers.
And then to blame it on the fact that he is the only one from SGU and doesn't want to attend with the guys/gals from SG1 and SGA (like they are the enemy or something) is just feet-stompingly childish.
It is hard to believe that some fans will just prostrate themselves at his feet and beg him and feed his immature ego like this.
Tell him to man-up dude! Honor your commitments and delight your fans. Make new fans for your new show with a cool con experience and convince the old show fans you have a product to offer they will like!
I fully expect this post to be deleted and I feel bad if it is hurtful, but it is my honest gut reaction to this news.
Sorry.