Whether it happens or not depends heavily on the results of the upcoming House of Councilors elections, but Prime Minister Shinzo Abe has clearly announced his intention to make amending the Constitution a campaign issue.
Although his Liberal Democratic Party issued a comprehensive amendment proposal on April 28, 2012 (the 60th anniversary of the end of the U.S. Occupation, unless you are in Okinawa or the Ogasawara Islands), Abe is trying to appear reasonable by focusing just on amending the amendment process. Currently, Article 96 of the Constitution requires that a proposed amendment first be approved by two-thirds of both houses of the Diet, followed by a majority of voters in a national referendum.
The line taken by Abe and his co-reformers is that the two-thirds threshold is too high, making it impossible to even get to the point of discussing possible amendments. As if on cue, the mainstream press has obligingly printed mendacious stories about how abnormally difficult the Constitution is to amend compared to in other countries. (It's not; anyways, constitutions are meant to be difficult to amend — it's one of the things that makes them constitutional.)