I currently have xsane and xsane-gimp version 0.999-6.1 installed. Now, world/xsane and world/xsane-gimp is at version 0.999-6.
Why a downgrade of $pkgrel?
I should assume that I should never downgrade: When there are issues which have been fixed or when a rebuild is necessary, $pkgrel, $pkgver or $epoch increases.
Regards!