What is happening in the last scene?

From the screenplay for THE WARRIOR, written by Gavin O'Connor and Anthony Tambakis & Cliff Dorfman:

INT. BOARDWALK HALL ARENA CAGE - SAME

Frank makes eye contact with the jubilant Tess. Indicates she should meet them in the locker room. Meanwhile, people pour into the cage. Frank pushes them aside, keeping them away from Brendan and Tommy, who remain on the ground, exhausted. Tommy to begins to WEEP.

INT. COLT’S PITTSBURGH FIGHT CLUB - SAME

Silence at Colt’s. Everyone spent from what they’ve seen. ON TV SCREEN: CHAOS IN THE RING. BRENDAN HOLDS TOMMY IN HIS ARMS AND PUSHES AWAY A DOCTOR.

INT. BOARDWALK HALL ARENA CAGE - SAME

Tommy buries his head in Brendan’s chest. A torrent of sobbing gushes from him, years of pain pouring out in heavy bursts. From the crowd, Paddy stares into the cage and watches as Brendan comforts his little brother, then helps him to his feet.

Callen, Sheridan, and J.J. Riley make their way inside for the post-fight interview, cameras trailing behind them. With Frank continuing to run interference, Brendan pushes through the crush of people, arm around Tommy, and exits the cage.

The crowd parts for Tommy and Brendan. Paddy watches them, a tear in his eye. He’s overwhelmed by the sight of his two boys together again.

As the noise from the arena fades, the brothers walk through the wild crowd and continue on through the tunnel, arm in arm...

Based on that and repeated viewings, I believe all that's happening is the ref wants to get Brendan up to declare him the winner, but Frank is telling him to let Brendan have his moment with his brother (Tommy tapped out, so the winner is obvious). There's no scheme to help Tommy escape; it's safe to say he'll be taken into custody shortly, but director Gavin O'Connor wisely chooses to end on a triumphant note of brotherly solidarity rather than the downer of Tommy getting arrested. A great ending to a great movie.

I believe in the end Brendan split the 5 million purse with his brother. I believe this to be what is transpireng in the inaudible ending. I see (after at least 30 viewings of this movie and myself trying to figure it out) Frank approaches Brendan and Brendan is hovered over Tommy in protection., Brendan tells Frank he wants him to ask Tess if they can split the money with Tommy, Frank ask Tess, Tess agrees nodding, Frank then approaches a couple reffs and the man who created and funded Sparta in my beleif letting everyone of them know of Brendans wish to split his winnings with Tommy and Mannys widow This was an absolutely amazing movie with every emotion touched. Nolte gave an Oscar winning performance. The plot the complicated relationships the things left unsaid and left up to the viewers own speculation and conclusios is what drew me so personally into the lives and dynamics of this family. Everything was not said not mapped out and neatly concluded by the writers. This was authentic and beautifully emotional for me the viewer. If if I could give it 10 friggin stars I would!!!!!

I don't think Tommy will get arrested after the story Manny's wife told CNN about American soldiers firing on Tommy's unit killing all of them. Also he saved those guys in that tank. So, if he does get arrested, they might shorten his sentence.