Sega was helping SNK after the fall of Aruze, but it was not really Sega who has managed to work with/help SNK, Dimps or Arc System Works... it was actually Sammy who has brought it all to Sega.
Sega had a policy to not make 2D fighting games, but they have released it all due to Sammy having already developed some titles on the Atomiswave era. Sammy have made a lot of deals with these companies before merging with Sega...so... Sega just ended up what Sammy has started.
Last year Sega gave(sold??) back the rights over the franchises Rumble Fish and Guilty Gear (and who knows which else...) to their respectives developers.
SNK has announced recently that they have quit with the developmente of new games. Oh, they are dead...
Well, SNK is not SNK since the koreans have bought them long time ago... Playmore is a korean company. They are only using the brand name "SNK" to appeal to the public.
Sadly, SNK has no future and would not help Sega on nothing.
If I had money and was Sega's owner, I would love to buy SNK though ;p