It wasn't too long ago that Robert Downey Jr. had painted himself into such a bad corner that much of Hollywood considered him unemployable. Nowadays, with his personal substance-abuse struggles behind him, his inspiring comeback story has positioned him as the king of two major franchises.

"I've got my hands full with all kinds of fun stuff," the "Iron Man 2" star told us recently. "I'm going to do 'Sherlock 2'; it was one of my favorite experiences to date."

If you told somebody five years ago that the same actor would play billionaire arms manufacturer/ superhero Tony Stark and 19th-century British sleuth Holmes, they would have called you crazy. But last December, Downey followed up on his "Iron Man" heat by releasing "Sherlock Holmes," which opened with $62 million at the box office and would eventually earn more than $200 million.

"It's hard to say," Downey admitted when asked if everyone -- particularly Rachel McAdams' character -- would be back for the sequel. "Because Irene Adler only appeared in one of the stories of Doyle's reservoir of activities. But we'll find out quickly."

As big a success as "Iron Man" was, Downey is convinced that the May 7 sequel improved on the original's formula. He feels similarly about "Sherlock Holmes 2."

"There's always [room for improvement]; as a matter of fact, that's the great thing about seeing a film in success," he explained. "A film in failure, you only see exactly what the audience thought was wrong, or it's your fault and you need to regroup. With 'Sherlock,' we both had success and the audience responded to it, and we saw room for improvement."

Although Downey doesn't know a great deal about the sequel yet, he did reveal that there are plans to take Sherlock's show on the road. "Yes, I think we'll be abroad," he said. "A bit of Paris, a bit of Switzerland by the end, if I'm not mistaken."

And as with any blockbuster these days, the next question is elementary: Will it be in 3-D?

"It's hard to say," Downey reasoned, following up on comments by the sequel's writers that talks have indeed included the possibility of going three-dimensional. "Certainly, if you don't do it as an option, then you don't have that option. If the last six months have shown anything, it's that audiences like options, and they will take advantage of them. And you're leaving a bunch of dough on the table if you don't shoot something in 3-D."

Do you think "Sherlock 2" should be in 3-D? Let us know in the comments!

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