If you need it now, buy now. If you can wait, .... wait.
The white Unibody MB will not see a drastic specs update when the next refresh comes, as it is aimed at consumers without much demand on those specs.
The current generation will perform well with most tasks like browsing, writing text in whatever application that supports any kind of text input, video watching, editing of not so complex short films, ... .
MRoogle might deliver you some more information, as your question gets asked a lot and you haven't stated your specific uses yet.