It's pretty hard to imagine what more they (the Russians) could do that they haven't already... for the last few hundred years or so. Nukes, perhaps?
This guy Umarov is not to be taken lightly. He's been at it with the Russians for a long time (1994), and I have to believe the KGB would be far more "aggressive", shall we say, than our guys would be, in trying to find and take him out. He's right on Russia's doorstep, too, in an area in which they claim authority (for all intents and purposes.) Yet Umarov has survived so far. Further, unlike Osama Bin Laden, his reasons for hating the Russians are intensely personal: If you read his bio on Wikipedia, well... I would not target innocent civilians if an occupying force had "disappeared" several of my family members, but I sure as heck would not take it passively.
Sochi is quite interesting. The good includes the resorts, beaches, and the climate. Per Wikipedia: Sochi has a humid subtropical climate[24][25] with mild winters (average 11 °C (52 °F) during the day and 4 °C (39 °F) at night) in the period from December to March and warm summers (average 24 °C (75 °F) during the day and 16 °C (61 °F) at night) in the period from May to October. Geez...
The bad includes it's proximity to problem areas. I also can't imagine how one could make such an extended urban area secure without turning it into something like East Berlin was in the '70's: "Greater Sochi" is 90 miles long. An attack would not need to hit the Olympic village or venues to be effective -- instead Umarov's group could target something 30 miles away where they can cause a lot of casualties. It will still be reported as an attack on Sochi. The Russians may have their hands full, I am afraid.
Going to be an interesting Olympics.