I have put 1.6.0 into package.mask for now. Because of the split of the ant-optional tasks to a separate package, we have to verify everything in the tree will build against ant w/o ant-optional first before we take it out. For the things that don't, we have a problem. 1. You can either make the ebuild dep =dev-java/ant-1.5.4 ...or 2. Hack the ebuild to detect ant-1.6.0 and merge ant-optional. Either way let's discuss it and make sure the packages in the tree are tested before we take it out of package.mask. Otherwise we may find bugzilla spilling over with new bugs... :)
If you need an example -- look at dev-java/jswat. It uses the optional PropertyFile task.
Ant 1.6.1 is live baby.