Note that even though I'm a SUP employee, I'm not allowed to comment on any of this officially, so for now I'm just compiling stuff that is otherwise publicly available on news sites.
PART 1: late 2012
* Dmitry Malov appointed the new SUP CEO
* The position of President no longer exists, Annelies van den Belt is now Executive Director of International Development
(Russian)
http://www.kommersant.ru/doc-y/2134530 "Alexander Mamut diluted his soup"
(English)
http://www.sup.com/en/management.html "SUP Media > Management"
PART 2: March 2013
* SUP merged with Rambler-Afisha
* both companies are basically big holdings with lots of projects
* the merged company is third best in Russian in terms of traffic
* Mamut will manage the merged holding
(Russian)
http://lenta.ru/news/2013/03/28/sumbler/ "Rambler-Afisha is merged with SUP Media"
(Russian)
http://lenta.ru/news/2013/05/17/final/ "The merger deal is now finished"
(English)
http://thenextweb.com/insider/2013/03/28/a-big-shift-in-the-russian-online-media-landscape-rambler-afisha-merges-with-livejournal-parent-sup-media/ "A big shift in Russian online media: Rambler-Afisha merges with Livejournal’s parent SUP Media"
PART 3: April 2013
* It is reported that Rottenberg brothers are creating a media holding that will include LiveJournal
* This turns out to be a hoax; the new owners of LiveJournal deny it
(Russian)
http://izvestia.ru/news/548902 "Arkadiy and Boris Rotenberg are creating a media holding"
(Russian)
http://lenta.ru/news/2013/04/19/nosell/ "Interros and A&NN deny that media assets are sold to Rotenbergs"
PART 4: May 2013
* The merged company gets top managers
* CEO: Petr Zakharov, who brings in 15 years of experience working in Apple
* CTO: Alexander Kononenko (don't know much about him)
* Who will manage product development is yet to be decided
* The general direction of company development will be to try and integrate the different services the merged holding has
(Russian)
http://www.gazeta.ru/business/news/2013/04/19/n_2864517.shtml "Petr Zakharov appointed CEO of the united company"
(Russian)
http://ria.ru/economy/20130521/938652463.html - same thing
(Russian)
http://www.gazeta.ru/business/news/2013/05/30/n_2943213.shtml "The united company gets the management"
PART 5: unknown
* According to livejournalinc.com, LJI doesn't have people working in operations anymore
* To my knowledge, it isn't publicly commented who handles this job now
(English)
http://livejournalinc.com/team.php "LiveJournal Inc. - Team"