CNN reports that an analyst (Colin Sebastian, Senior Research Analyst, Internet and Interactive Entertainment, at Lazard Capital Markets) predicts that Sony will cut PlayStation 2 prices from $149 to $129 by the end of April.

Sony declined to comment on this topic.
It is very likely Sony will squeeze the last drop out of their hyper successful Sony PS2 console by dropping its price before the Sony PS3 will hit the market.
A $20 price-drop is not really a lot. Early rumors actually suggested a price-drop of the PS2 to $99. Going under $100 would definitely show some reaction with consumers. The last price-cut for the Sony Playstation 2 was back in 2004.
Sony recently announced a price-drop for the Sony PSP by introducing a Sony PSP Core package.