Radiohead keep plans very close to there chest. It's pretty much expected that the band will do more dates but it will be about as secretive as the current tour.
Wouldn't be shocked to see them at cochella next year.
New album went to number 1 and if there did announce a large uk tour I'm fairly certain it would sell out quickly. A moon shaped pool has done quite well commercially , be interesting to see if there do try and do a larger tour next year.