If you have installed smeserver-ejabberd version1, you cannot upgrade with ejabberd 2.0.0 . You'll have to wait for smeserver-ejabberd-2 release, which will import itself ejabberd 2 and erlang during the yum upgrade.
smeserver-ejabberd 2 is presently in test.
There is a major difference beetween smeserver-ejabberd v1 and v2.
V1 rpm includes a binary installer of ejabberd (and erlang), and V2 relies upon external ejabberd2 and erlang rpm (coming or updated from EPEL repo).
So ejabberd and erlang rpm are presently in smecontribs repo because there are needed by smeserver-ejabberd v2 version.
Upgrading only with these rpm is not possible.