Photokina is the biggest show for photography equipment that takes place every 2 years in Cologne, Germany. This year Photokina will be between September 21- 26. Here is a summary of all rumors, predictions and expectations for the main players in the industry:
Canon: Canon G12 is a given, based on previous release patterns (they release a new version every year in September). Low chance for a new small/compact DSLR. Pictures of the Canon 60D are already available online, so you know that one is coming. There could be more PowerShots cameras like the S95, SX30 and SX130. I am sure that Canon will also release new lenses as well but I have not idea what exactly.
Panasonic: a new GH (probably called GH2) and a new GF cameras (the GF1 was announced in September, 2009). New m4/3 lenses are also expected: 14mm f/2.5 and the 100-300mm lens.
Olympus:Olympus E-3 successor is certain and probably a new PEN, since they are on a 6 months refresh cycle: the E-P2 was released in November 2009, the E-PL1 was released in May, 2010 - you do the math.