It was supposed to be 10, they bumped it up to 13, with the longer run times it will probably be like 17-18 normal length episodes.
So really, we should be glad we're at least getting that and not 10.
No, we should demand that they not neuter the show's pacing for no real reason at all. "It was supposed to be 10..." uh... says who? That doesn't refute what I just said. This is all a decision and the decision should be based upon keeping the show consistent in quality. There's no law in place that says Game of Thrones couldn't be more episodes or even more seasons. Again, this is the most popular show on air. I'm 100% sure HBO themselves want more. It was the show runners that said they didn't need it, presumably because they could keep up the quality. Well, they didn't. You can't use episode count to excuse their decisions, because that was also their decision.