Re: Who is more likely to win another GS?
Tough to say. While Roddick is getting old, he is still a couple years off from being 30 and all he honestly needs is a good tournament where he is just unstoppable on serve such as at Wimbledon this year and he can just relax and take chances on the returning game, and this scenario is still very possible. While Djokovic hasn't been as successful as his Australian Open win last year, he has still be very solid on the tour for the most part with his wins at Indian Wells, Rome, TMC, Dubai and his run from good runs at Miami through Madrid this year and he has had at least some Grand Slam success at last year's US Open along with Aussie Open and Wimbledon this year.
Honestly I think it is really tough for Djokovic to do much because he really doesn't have one really big weapon that stands out. I mean you could say his backhand, but it definately is not Nalbandian-esque. As John McEnroe said, he felt as though when Djokovic and Safin played last year at Wimbledon that Novak plays very similar to Safin except that he is more of a lightweight. He probably packs a little more power overall than Federer, Nadal, Murray, but like I said, there isn't any part of his game that really stands out so in a way I think it is tough for him to step it up because he needs his whole game to be on rather than one or two weapons. Could be mental or whatever, but it has become tough for him since last year's Aussie Open. Roddick still has a chance as well in my opinion but like I said, it will really have to be depending on his serve. Not saying he is "all-serve," but it does play key to when he returns.
Federer / Haas / Safin / Gaudio / Kuerten / Youzhny / Nadal / Gonzalez / Ljubicic / Hewitt / Soderling / Wawrinka / Coria / Nalbandian / Kohlschreiber