I think he said it while promoting Tintin but I saw him say that he thought that Jurassic Park was the one movie of his that he thought would work as a 3D conversion so I'm sure he's involved (and while Universal can legally do what they want, I doubt they'd go ahead if he was unhappy with it)...
I just read that the first movie is getting converted to 3-D for its 20th anniversary next year so maybe they'll do single releases (or the sequels if Kevin is correct about the first one coming out this year) then as a tie-in.