This step how to update you clamav to the latest version using OpenBSD Ports :
Extract OpenBSD 4.4 ports packages, should be ports.tar.tgz , extract it to /usr/ports
use this command
#tar zxf ports.tar.gz -C /usr
Delete the clamav ports tree , we should do this because some patch from original OpenBSD 4.4 ports will make conflict with the newest clamav version (0.94.2)
#rm -rf /usr/ports/security/clamav
Now , get some OpenBSD CVS to get the news clamav ports source
#export CVSROOT=anoncvs@anoncvs.ca.openbsd.org:/cvs
Get the clamav ports source
#cd /usr
#cvs -q get -P ports/infrastructure/db/user.list
#cvs -q get -P ports/security/clamav
Then Compile it :
#cd ports/security/clamav
#make install
The news clamav now in your OpenBSD box 
I have tried to update the ClamAV on OpenBSD 4.8 by your method:
# cd /
# export CVSROOT=anoncvs@anoncvs.ca.openbsd.org:/cvs
# cd /usr
#
# cvs -q get -P ports/infrastructure/db/user.list
The authenticity of host ‘anoncvs.ca.openbsd.org (142.244.12.42)’ can’t be established.
RSA key fingerprint is 20:ad:fa:70:cf:85:54:9d:ee:7f:6c:a3:98:77:94:4e.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added ‘anoncvs.ca.openbsd.org,142.244.12.42′ (RSA) to the list of known hosts.
U ports/infrastructure/db/user.list
# cvs -q get -P ports/security/clamav
U ports/security/clamav/Makefile
U ports/security/clamav/distinfo
U ports/security/clamav/systrace.filter
U ports/security/clamav/patches/patch-clamd_Makefile_in
U ports/security/clamav/patches/patch-database_Makefile_in
U ports/security/clamav/patches/patch-etc-clamd_conf
U ports/security/clamav/patches/patch-etc-freshclam_conf
U ports/security/clamav/patches/patch-etc_Makefile_in
U ports/security/clamav/patches/patch-libclamav_Makefile_in
U ports/security/clamav/patches/patch-libclamav_mbox_c
U ports/security/clamav/patches/patch-libclamav_ole2_extract_c
U ports/security/clamav/patches/patch-libclamav_str_c
U ports/security/clamav/patches/patch-libclamav_vba_extract_c
U ports/security/clamav/pkg/DESCR
U ports/security/clamav/pkg/PFRAG.shared
U ports/security/clamav/pkg/PLIST
U ports/security/clamav/pkg/clamav_daemon.rc
U ports/security/clamav/pkg/clamav_freshclam.rc
#
# cd /usr/ports/security/clamav
# make install
===> Checking files for clamav-0.96.5p0
>> Fetch http://downloads.sourceforge.net/sourceforge/clamav/clamav-0.96.5.tar.gz
clamav-0.96.5.tar.gz 100% |*******************************************************************************************************************************| 40200 KB 03:25
>> (SHA256) clamav-0.96.5.tar.gz: OK
>> Broken dependency: empty directory (DEPENDS devel/check)
*** Error code 1
Stop in /usr/ports/security/clamav (line 1765 of /usr/ports/infrastructure/mk/bsd.port.mk).
*** Error code 1
Stop in /usr/ports/security/clamav (line 2168 of /usr/ports/infrastructure/mk/bsd.port.mk).
*** Error code 1
Stop in /usr/ports/security/clamav (line 1580 of /usr/ports/infrastructure/mk/bsd.port.mk).
*** Error code 1
Stop in /usr/ports/security/clamav (line 2136 of /usr/ports/infrastructure/mk/bsd.port.mk).
*** Error code 1
Stop in /usr/ports/security/clamav (line 2116 of /usr/ports/infrastructure/mk/bsd.port.mk).
*** Error code 1
Stop in /usr/ports/security/clamav (line 1611 of /usr/ports/infrastructure/mk/bsd.port.mk).
*** Error code 1
Stop in /usr/ports/security/clamav (line 2116 of /usr/ports/infrastructure/mk/bsd.port.mk).
Something wrong
I am sorry vlader, my experience, a openbsd version will have their ‘unique’ way to install ClamAV on it, right now I have no 4.6 OpenBSD Server so I can not test new ClamAV