As far as i know Terry has stopped signing due to his embuggerance (altzeimers) and any recentish 'signings' have involved thumb prints rather than actual signatures. As he is currently working really hard on the Long Earth book i don't think any signings will happen before october if at all.
'There is no future for e-books, because they are not books. E-books smell like burned fuel.'
Ray Bradbury (RIP)