A good example of what I WANT a Warriors movie to be like is an old animated show called The Animals of Farthing Wood. nice hand-drawn animation, with fitting dramatic music and death! (seriously, look up 'animals of farthing wood deaths', there's quite a few of them).
But these days, they probably wouldn't be able to get away with killing so many characters in a movie for children. And think of all that blood in the books. You'll get kids asking their parents why the kitties are covered in ketchup.
They'd either have to remove quite a bit of the violence or aim the movie (oh gosh how many times have I said the word 'movie') towards an older audience, and then they're not going to get as many people watching.

Another issue - there's going to be cut content.
There are just so many characters in Warriors, they'd have to remove some or merge some together. Some examples (as Youtubers have already suggested) are Darkstripe and Longtail, Lionheart and Whitestorm, or Cinderpelt and Cloudtail. Mixing these characters together would ruin them.
And I'm sure they'll be cutting unimportant scenes as well, otherwise these movies will be WAY too long. (I've got my copy of Into the Wild here and it's 303 pages long.)
Also there's about thirty-six books in the main six series (if you include Dawn of the Clans). Thirty-six movies? I think not. But Heyman said, they'll keep on making movies as long as they have interesting stories to tell and the audience likes 'em *shrugs*

And the last thing I've got to talk about: how will it change the Warriors fandom?
I'm worried that getting an official movie will ruin some of the creativity of the fandom. Right now everyone has their own way of drawing the characters. But I feel like if this movie comes out, people will stop using their unique designs and stick with the official ones.
And I think there'll be less fanmade animations - less MAPs and AMVs and such.

But hey, we don't know if this movie will even become a 'thing'. It might not ever be finished.
Let's just hope that if it does happen, it won't be a complete disaster!

That's all for now. *bows and walks off* Comment if you want.

Those are some sharp observations, I agree with all of them.
I wonder if they will just write an entirely new story. They might take some old characters, maybe new ones too, and create a new plot that can fit into a single movie, and in the process limit the number of violent scenes. You never know.

Those are literally all of my concerns- If I were them I would stick to the books, even if it made the movie 5 hrs long and was 'R' rated

Part of me hopes that they use a different story with different characters, not canon characters, so they dont mess up the books

*screams internally* wow there's a warriors movie? we don't have any of THOSE yet *glances at all the crud on youtube that you see when you search 'warrior cats')

I'm just glad they will at least do into the wild.
Cause ssswarriorcats never updated X-X