Sirius Black

ok Sirius Black isn't dead nobody knows but J.K. he was hit with a red spell blocked it then hit again but we dont know by what he fell through the portrait. I'm saying he got stunned and fell in the portrait. Later in book 5 Harry got told that the reason that portrait was in the Department of Mysteries is because what ever fell through there never returned. well in book 7 i'm guessing Sirius comes back because he finds a way out or somebody at the Department does. You say "why would J.K. bring him back anyways" why wouldn't she he's much more help to harry then two 17 year old teenagers

Sirius fell through a veil, not a portrait.

Plus with the second spell from Bellatrix's wand we aren't told what colour it is. I know that for the first one we're told it's red. It might be implied by the first one's colour that the second spell was meant to be red, but then it could have been any spell colour. Admittedly, reading between the lines of the death scene Sirius doesn't die the way you'd expect someone to when they got hit with the Avada Kedavra. I mean when someone's hit with that spell don't they just slump over and die? But the description we're given of Sirius being hit in the chest suggests a slower death, his facial expressions suggest that he had time to register that he had been hit with a spell that killed.

If Sirius is still alive then why J.K did'nt tell it at the 6 th harry potter why he would survive at the 7 th book?

We still don't really know anything about that archway.
Just vague hints.
Lupin THINKS he knows something and honestly believes that Sirius is dead.
Still, it's in the department of mysteries. It's a mystery.
Probably no one knows.

The mood, the writing style, the absence of clues, make me believe
that Sirius will stay dead. But who knows?

A gingerbread ending? Any death in which they never found the body is fair game.
What might JKR do? She's sent out so many contradictory clues,
I wouldn't put anything past her.
Like Narcissa said, "There's nothing I wouldn't do any more."

How would Sirius find a way back through the the Archway if nothing comes out of that?
Sirius is definately dead.

I was hoping (and still do) that JKR explains about the veil in book 7, but I'm getting the feeling (no particular reason, just am) more and more, that she isn't going to explain it at all.

Nope, she never got around to explaining that one, either.
How can she imagine that anyone would be satisfied with that last book?

Well, i liked DH. but i think u're right Psy, there r many questions which remain unanswered