Just because Disney buys Looney Tunes doesn't mean that they have to buy warner bros. Disney bought the Muppets and bear In The Big Blue House, but they didn't buy the rest of the Jim Henson Company.
If Disney did just buy Looney Tunes, I wonder what kind of problems there would be including copyrighted characters. Disney would own all of the shorts, all of the television series, all of the movies, all specials, and possibly Tiny Toon Adventures, but they probably wouldn't own Anamaniacs even though the Looney Tunes made frequent cameos on that show. Disney also wouldn't own warner brothers movies that had cameos by the Looney Tunes, like My Dream Is Yours, Two Guys From texas, and Gremlins 2.