We're all wondering who exactly the Red Hulk (Rulk for short) is,we are told that it will be reveled in either FALL OF THE HULKS or WORLD WAR HULKS but I think I know the answer.  
I think the red hulk is EMIL BLONSKY aka the ABOMINATION. 
Just hear me out. I know that he was killed by Rulk in issue 1 
  
 but you have to think about whats happened since Hulk since issue 600 where we learn from She Hulk that after World War Hulk Bruce was taken to a secret Gamma base which Sampson and She-Hulk were told was a shield bunker but were experimented on by M.O.D.O.K and according to COMICVINE the last place we see the Abomination before Hulk issue 1 is being imprisoned in a military installation because he killed Betty Ross, it could be the same gamma base 
They could have separated Blonsky from the Abomination and turned him into the Red Hulk in exchange for killing Hulk. 
General Ross:  
    
Says this to an unconscious Rulk 
      
Which could means they could have given him everything he needed to kill the abomination as well which could have been weakened after they were separated and in Hulk issue 12 Rulk tells Hulk after he is reunited with a dead Jarella that I REALIZE NOW I'VE LEFT YOU WORSE OF THAN DEAD WITH A BROKEN HEART. JUST LIKE YOU LEFT ME BANNER... This could be a reference to the time when the abomination was forced to watch a recording himself and his wife Nadia when he was in jail or when Hulk shrunk down to a small size to try and convince the Abomination to let her go when he held Nadia captive. 
Think about it , why would Jeph Loeb make Rulk kill the Abomination the very first thing he does in Hulk number 1 
To give him an alibi like in watchmen when Ozymandias ordered a hit on himself so no one would suspect that he killed the Comedian 
Its just crazy enough to make sence