Pro Evo Live League UK announced that up to 4 players (2 vs 2 or 3 vs 1) will be able to play online in Pro Evolution Soccer 2009. This is what they have posted at their forums :

"Yep that's right, 2vs2 is definitely in pes2009 online. We suspected before, but it's now a definite. With regards to "become a legend" online, they are still working on it and are yet to make a final decision on the maximum numbers due to connection/lag issues."