Hello, mupdf-1.9 has been available since 2016-04-18 (http://mupdf.com/news).
commit 9d40bc9df5cd1c5de3bcdd0d6e846ae832ede27b Author: Michael Weber <xmw@gentoo.org> Date: Sat Jun 4 21:45:29 2016 +0200 app-text/mupdf: Version bump (thanks johncarmack@cock.li for the hint, bug 584266). Package-Manager: portage-2.3.0_rc1 app-text/mupdf/Manifest app-text/mupdf/files/mupdf-1.9a-CFLAGS.patch app-text/mupdf/files/mupdf-1.9a-debug-build.patch app-text/mupdf/files/mupdf-1.9a-no-thirdlibs.patch app-text/mupdf/mupdf-1.9a.ebuild