Just recently, emul-linux-x86-db was introduced to provide 32-bit libs for varios DBs and ODBC, with explicitly mentioning wine. See bug 308905 I couldn't find any database related RDEPEND of wine though.
Fixed in 1.4_rc4, thanks for reporting. >*wine-1.4_rc4 (21 Feb 2012) > > 21 Feb 2012; Alexandre Rostovtsev <tetromino@gentoo.org> > +wine-1.4_rc4.ebuild, wine-9999.ebuild: > Bump, see http://www.winehq.org/announce/1.4-rc4 for the announcement. Add > /usr/bin/wine and wine-preloader symlinks for win64-only installs (bug > #404331, thanks to Zhang Hongjiu). Add odbc USE flag to pull in unixODBC > runtime dep (bug #404507, thanks to Andreas Sturmlechner). Use pax-mark (bug > #375797, thanks to Anthony Basile) and mark win64 binaries (bug #404329, > thanks to Zhang Hongjiu). Add a die in src_configure when intel opencl is > selected to help with bug #403947 (thanks to candrews and Kacper Kowalik).