As you probably recall since it wasn't that long ago, Titanic made something like a gajillion dollars(actually $1.8B plus 11 Academy Award wins) when it came out back in 1997, and thrust Leonardo DiCaprio and Kate Winslet into the hearts of millions of people who kept coming back for more of the tragic love story. Cameron would go on to best Titanic's final tally with Avatar's crushing $2.8B total. Remarkable. If there's anything Titanic needs it's more cash. Gotta fend off that pesky Lord of the Rings: The Return of the King that keeps trying to nip at it's heels for 2nd place.
The April 6th release date was chosen for a reason as the ship made it's maiden voyage to New York on April 10th, 1912. The sinking didn't actually occur until four days later on the 14th.
Cameron, who has in the past derided the use of post-converstion 3D except in the case of "classics" seems positively ecstatic over the planned release...
"There's a whole generation that's never seen ‘TITANIC’ as it was meant to be seen, on the big screen. And this will be ‘TITANIC’ as you've never seen it before, digitally re‐mastered at 4K and painstakingly converted to 3D.
With the emotional power intact and the images more powerful than ever, this will be an epic experience for fans and newcomers alike."
You're not going to see many re-releases that will pack as much punch as Titanic. In fact, I expect that there will be some other flicks due to release that week that might get shuffled around. Not that anyone expects Titanic to gross another billion dollars, but is $150M possible? Maybe more? It's definitely in the cards.