Without having seen the movies, I can't know for sure. But the impression I get from the trailers is that the intention is that they're designed so that you could view them in "chronological" order (i.e. Hobbit first, followed by LotR).
To achieve that requires some hackery of The Hobbit, which is really better thought of as a different story in the same universe. The storytelling styles are very different, and there are some conflicts that are understood as being the result of different narrators (and a somewhat unreliable one, in the case of The Hobbit).
The information we have on the Hobbit movies suggests that he's trying to harmonize them, making them fit more seamlessly together, and more in the style of the films set later in Middle Earth history. So, you could view them as five-movie series, in that order, if you wish.
But I don't think that the LotR films would particularly benefit from it. They contained all of the necessary story within themselves, and in fact, some of the flashbacks will be kind of inconsistent. I do suspect that they're going to some day rerelease a modified version of the LotR movies, with Martin Freeman as a young Bilbo rather than a heavily-made-up Ian Holm, and I really wish they wouldn't.
As for the converse question, of whether the Hobbit films will really stand on their own without LotR ... I'd imagine that they could be seen that way. Although, they do appear to be trying to merge it in with the series more than The Hobbit does, and I suspect a few moments will be subjected to ominous foreshadowing that the book doesn't contain, I'm sure that the films will be intended to make complete sense without it.
Still ... it will help explain what is surely going to be ominous music when Bilbo finds the ring, and it'll help to know why they're making such a big deal out of Legolas (who doesn't actually appear in the book by name, though he can be inferred to have been present).
More questions on The Lord of the Rings (books, movies and creative franchise):
- Are Bilbo Baggins and Pippin Took related?
- Does Sauron know that Frodo has the Ring and is attempting to destroy it?
- In The Hobbit, how similar are dwarves and dragons?