It's from Nintendo, so unless Nintendo stops making hardware like Sega, there's no way Pokemon will come to the PS2. But there are alternatives. I think Digimon, and other games that have monster raising is on the PS2. I forget which games but they're there I'm sure.
As others have said, the Pokemon Company is owned by Nintendo, so you have a better shot at hooking up with Angelina Jolie and Jessica Alba at the same time then you would at seeing Pokemon on Playstation or Xbox.