limits of regular expressions

Hallo NG,
 
If the task would be to represent an ISBN-number with a regex 
would you agree that this can´t be done sufficiently with the current
version
of XML Schema regexes, because the last digit is calculated?
 
Is it planned to do something like this, perhaps in the next version?
 
Provided that the first assumption is true, can you think of other "common"
use-cases
that regexes can´t do yet?
 
Thank you
 
Rainer