I'm pretty convinced they will add more dates. They sold out in about 35mins max, it would be foolish and a tad disrespectful to the fans if they didnt.
I have a got a seated ticket at the Liverpool Echo gig, but really won't be able to stand going to a Muse gig and sitting down. So, if I can't get a swap I will be selling at a generous price...Because I <3 Muse fans