It's not a "next" it's a current branch of marketing. And yes I believe it will grow even more, but not to be THE next dominating channel. Day after day, more channels for advertising are being created and improved, and that's the only thing that will increase; the number and diverse of channels.
I agree with Mohamad, it is not the next generation, it has always been one of the best means of advertisement. Passing a message or advertising your product without your audience consciously noticing that you are and without it looking like an advertisement per se is a very common and effective way of "manipulating" consumers.
Content placement in TV shows and movies are useful in the way that it allow the audience to identify the product or service to characters or situations. It can also be a good way to finance the content by creating partnership with the brands. If the brands agreed to "invest" in your content you have more chance to get into the medias.
Just like product placement has proved to be extremely effective in influencing buyer behavior and increasing sales of the product, I think that content placement is 'the next big thing' in advertising. But again, I might be wrong.