That's the rumor, according to Comic Book Resources:
The big rumor of the day is from Latino Review, claiming they know who Marvel wants to sling the shield -- Leonardo DiCaprio. "Now before some loser film website goes out there and tries to debunk me let's get it straight," the site said. "Don't expect Marvel to go on the record and say 'Yes it's true, we are looking at so and so.' Hollywood doesn't work like that. Studios and production companies only go on the record to announce the casting of a role when it's official. I announced the lead in the upcoming 'Prince of Persia.' It took the trades weeks later to make it official. That being said ... NO OFFERS HAVE BEEN OFFICIALLY MADE! NOBODY HAS BEEN CAST YET! DICAPRIO IS PROBABLY CLUELESS AT THIS POINT!" Right then.
If we were to go from the perspective of looking like Captain America, Leonardo Dicaprio doesn't fit much at all. On the basis of acting ability, it doesn't much matter. Dicaprio doesn't look like Howard Hughes, but he gave a phenomenal performance in The Aviator. Marvel could do much worse than casting Leo.