I doubt that they will show both Katniss and Peeta w/ burn on their half of the body and how broken they are in the end of the movie since they don't have happy ending bec both of them are so broke and Katniss will always have depression, but scare that she will always look over her shoulder that she scare that her kids will be taken and Peeta couldn't tell the difference of what's real or not than seeing them being smiley and happy in love which I don't want that, but I prefer that they can stay to true from the book to movie, but nope..

Yes, I'm quite positive they will give them a much happier ending compared to what we had in the book, because if they would go further into that PTSD issue, they would need an extra movie to show us all the aspects of their recovery. In books is easier to proceed faster when you want to tell something big (that happened in a very long time) in just a few lines, but in movies you can:
a) make a montage - but that's a very 80's thing - or b) you need more time to tell everything, period. No way they can show us their growing back together AND Katniss depression in just 10 minutes (if not less). So yes, I'm sure they will pretty much skip that phase (her depression).

But that being said, I don't think the book didn't have its happy ending. To me the fact that they grow back together and in spite of everything they found each other again, means a lot. Katniss' final speech tells it all:

“What I need is the dandelion in the spring. The bright yellow that means rebirth instead of destruction. The promise that life can go on, no matter how bad our losses. That it can be good again.”

Being optimistic about a future where you believe you can be happy again, even after all the pain they suffered is impressive! Sure, they will always have their post-traumatic symptoms, but that's what life is, a compromise of what is good and what is bad and those final lines where full of hope and positive vibes to me. So even if rushed and a little bit bitter (but how could it not be?), their closure is happy in my opinion.

If they didn't have their happy ending, Katniss would have committed suicide, she tried at least twice. And Peeta would have ended up in the nut house for the rest of his life, seeing tracker jacker delusions of katniss trying to kill him. But the impossible happened. He remembered he loved her and wanted to protect her, just as she tried to protect him and she held closely to the hope she had the first time he saved her life. He was her dandelion, no matter how tragic their life is on the outside. It IS good, and as good as they could have ever hoped for under the circumstances.

I agree with what everyone is saying, I hope the ending is shown 'happy' but with that bleak undertone it clearly had in the book. This wasn't a typical happily ever after, it was two broken people who found a bit of light in their darkness and grasped that so they could keep on living. Every day is a struggle for them. That's something that's hard to convey in a short time on screen, especially since we haven't seen THAT much of how broken Katniss really is (in the movies).

I think that all we're gonna see of broken!Katniss was already shown in MJ1, it's likely that MJ2 will focus more on the war and her fighting attitude, I doubt there will be more space for her inner struggle. MJ1 was full of it and some people (usually non-readers viewers) complained about the lack of action, so I believe MJ2 will "make up" for that lack (which I really didn't feel tbh).