Opera announced that they are abandoning their own browser rendering engine Presto.
The Opera browser will be build on top of the Chromium browser (which is the basis for Chrome).
The freed developer resources from the Presto development are going to support the Chromium and WebKit projects.
IMHO this is good news for developers, because it means that you can avoid optimizing for an additional browser rendering engine and that the WebKit development will be pushed even more.
Opera recently reached 300 million users, so it is good to give these users a good experience with your application by simply optimizing for WebKit.