Interesting topic, Nathi.
I think we could see 3 Ukrainians into the top 100 next year, but not sure about the 4th...don't know enough about Sergeyev to be able to comment.
Stakhovsky has the ability to be a solid top 100 player, although I'm not sure how much better he could be...certainly, as far as rankings are concerned, he should have a realistic shot at top 50 in the first half of 2010, but I'm not sure that he could sustain that level.
I felt that Dolgopolov had some promise when I first saw him at the GBR/UKR tie in Odessa (2006?), and it is good to see him finally breaking through. He had good touch and feel for the ball...nice strokes. But I'm not sure how far into the top 100 he could go as I don't remember him having a big shot...and in today's game that is something you need.
Marchenko...very 'pushy' player when I saw him in that dreadful Davis Cup rubber against Goodall, and couldn't see him being better than top 100. Could add more weight of shot if he wants...has the frame to be able to do it imo. Otherwise, I don't see him taking many good scalps in the ATP events.