Hmmm the DS will beat it for sure, it is at 124m right now and has just sold 30m in 2009. Even given steep yearly drops, it will definitely pass the PS2.
The only other possibility is the Wii and it is a bit of a stretch. I don't think the Wii can pass the PS2 as it has much stronger competition than the PS2 and it does not have enough quality 3rd party titles IMO to sustain its sales and give it the legs the PS2 had. Unless the video game market grows greatly as a whole, I really doubt it will happen. It will get close, but most likely not pass it.