According to the latest newsletter, the roster of exhibitors who will be attending the gamescom is as follows:

1. Activision Blizzard
2. ak tronic
3. Atari
4. Avanquest
5. Bigben Interactive
6. BigPoint
7. CAPCOM
8. City Interactive
9. dtp entertainment
10. Eidos
11. Electronic Arts
12. flashpoint
13. GOA
14. HAMA
15. HMH Hamburger Medien Haus
16. Koch Media
17. Konami
18. marketpoint
19. Microsoft
20. NC Soft Europe
21. Nintendo
22. rondomedia
23. SEGA
24. SevenOne
25. Sony
26. SouthPeak Games
27. Square Enix
28. Take 2 Interactive
29. Tivola
30. Ubisoft
31. Warner Brothers Interactive Entertainment

As you can see, quite a lot of prominent exhibitors will be present at the gamescom in Cologne (which is the spiritual successor of the Leipzig Games Convention, but was also its rival for a time). The gamescom will begin on 20 August 2009. You can find more information on the official website.