If Plushenko deigns to formally appeal his competition ban, I think the ISU will probably let him compete. I can even imagine a scenario in which the Russian figure skating federation intercedes to the ISU on Plushenko's behalf to pleeeeeeease let him compete because without him our men's program is pathetic. Apparently even Alexei Yagudin expressed hope that Plushenko would be allowed to compete in Sochi, which is surprising and awfully classy of Yagudin because apparently between 1998 and 2002 he and Plushenko had quite a bitter rivalry going on. But anyway, I don't think the ISU will need too much metaphorical arm-twisting to let Plushenko compete again. His offense was relatively minor and in recent years the ISU has become increasingly lenient toward professional skaters seeking to regain competitive eligibility. Moreover, Plushenko is a controversial skater, and the ISU knows that controversy tends to bring in more spectators.
Apart from Plushenko, Russia's next best hope at an Olympic medal in men's singles is Artur Gachinski. Gachinski has apparently looked up to Plushenko for years and currently trains under Alexei Mishin, Plushenko's coach. During the Grand Prix series, the commentators kept remarking about how similar Gachinski's technique is to Plushenko's, specifically the catlike ability to land on his feet even on a poorly executed jump. The similarity between the two is quite noticeable and quite astonishing. I suppose that catlike landing ability is a valuable skill to have, but I think it would serve Gachinski (and Plushenko, if it comes to that) so much better in the long run to learn how to jump properly so that he wouldn't need catlike instincts to land them cleanly and could pick up more grade of execution points to boot. As long as Plushenko is not competing, this would be a perfect opportunity for him to rework his jumping technique so that he could correct those issues and potentially bring up his grade of execution marks because, in the event that he does end up competing in Sochi at the comparatively advanced age of 31, he is going to need all the points he can get.
Even if Plushenko does compete in Sochi, I don't foresee him winning another Olympic gold. I think that Alexei Yagudin is right that he is Russia's best, and possibly only, hope for a medal in men's figure skating in 2014, but I'd be very surprised to see that happen. Moreover, if he continues to skate the way he did in Vancouver (front-loading his program, landing borderline jumps, neglecting his program components, recycling his choreography, etc.), I would be shocked to see him on the Olympic podium ever again. If I were him (and I am thankful that I am not), I would forget about competition and go professional. I ran across a very enjoyable exhibition program he did last June, and it seems that when he's not concentrating on competing or obsessing (i.e., being a jerk) about the quad, he's actually quite a charming and charismatic performer. WARNING: The following link contains an upsetting muscle-suit picture. Apparently he also has a few other athletic career options open to him as well. I don't how serious he is about competitive table tennis, but I would pay good money to see him ping-ponging for Russia in London next year.
But back to men's figure skating: as to who WILL be on the podium in Sochi, I think it's pretty safe to say that at least one of them will be from Japan. Japan has a really strong program in men's and women's singles; in 2010, all four of the singles World Champions on the junior and senior level were from Japan. There are a lot of other strong contenders from the US and Europe as well as some promising talents from other countries/regions, but as of now, my pick to win the gold medal is Patrick Chan of Canada.
Patrick Chan is a two-time world silver medalist, and his recent victory at the Grand Prix Final was a game changer. He landed quads in both the short program and the free skate (a "gorgeous" quad toe loop in the free skate according to commentator Tracy Wilson, and I quite agree). His free skate score was a mind-boggling 174.16. His total score of 259.75 would have won him the Olympic gold medal by just over two points if he had skated it in Vancouver. He's certainly had his ups and downs throughout 2010 and he really needs to work to get his triple axel as consistent as his other jumps; nevertheless, I will be very surprised if he doesn't win the World Championships in March, and if he doesn't at least land on the podium at the 2014 Olympics, I will be shocked.