As Russia gets more involved with the Syrian civil war, it's likely that Sunni militants will intensify their campaign against Russia. But the key reason why Sunni attacks on Russia proper will increase is the fallout between Sunni jihadists in the Caucasus — namely, the al-Qaeda-linked Caucasus Emirate and the ISIS-linked Wilayat Qawqaz.
Russia is fast replacing the United States as the number-one enemy of Al Qaeda, ISIS, and other Sunni jihadist groups motivated by violent and puritanical Salafist ideology. This shift is rooted in recent Russian actions in the Middle East.
From the Black September attacks on Israeli athletes in 1972, to the post 9/11 games in Salt Lake City, to the 2012 games in London, security has been a concern at all modern Olympics. Recent terrorist attacks in Russia, though, present particular concern as the world's athletes descend on Sochi.
The Volgograd attacks have brought renewed world attention to the unresolved conflict in the turbulent Caucasus. The bombings no doubt have rattled Russian nerves. While Umarov's reputation among extremists will rise, President Putin's reputation as defender of Russia is at stake.
One doesn't need a clear link to a global terror group to carry out an attack; one needs only the resources, the means and an Internet connection. But the global nature of these communities and their online links also create openings police can exploit.