Are there any plans to implement this functionality?
Yes, you can close this issue.
This functionality appears to have been implemented by DERBY-2631. If so this issue could be closed.
Correction : The original was using IDENTITY columns as the native generator, but Gavin ran into problems using IDENTITY support.
From what I can tell, this was not a modification but rather the Dialect as given to us by Simon Johnston. If y'all feel that some aspect of that Dialect is not correct, than by all means let us know what should be different.
It appears that the hibernate folks have modified the DerbyDialect to use a TableHiLoGenerator as the "native" identity generator in lieu of the IdentityGenerator to circumvent this problem.
I've posted a question on their JIRA here: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1915