It's all over the web, but the sole source is Digitimes, which has been wrong about so many things, I'd almost take this as solid evidence that a 15" MacBook is not coming.
I haven't heard much of anything about it... I honestly can't see that happening. If anything I could see a 13 or 12 inch MBP...The whole idea of the Macbook is it's tiny-ness, price point, and its appeal to lower-end use (word processing, some minor photo editing, web browsing, etc).
I don't think we've heard anything about that here... I would expect a 13" or 12" Macbook Pro before a 15" Macbook... but what do I know? I've been wrong about things before...
Of course, that means it's completely incorrect. What is more likely is they have misinterpreted news that Foxconn will be building 15" MacBook Pros as a supplementary supplier to Asus and run with the news as "Foxconn to build 15" MacBook model" - if we're to believe Digitimes then the G5 PowerBook and G5 iBook models are now over a year late, and they were dead certain Apple were going to release them.
And besides, there's really no room in the line-up between the BlackBook and the MacBook Pro for a 15" MacBook.