Philip Seymour Hoffman was offered the role in early June, and it looks as though his negotiations have all wrapped up.  Plutarch Heavensbee doesn't play a huge role in the novel, but becomes considerably more important in the finale novel, which is expected to be divided into two cinematic halves, like the finales for the Harry Potter and Twilight franchises.  All things considered though, it's likely that the character will be more directly involved in Catching Fire, just as Seneca Crane, played by Wes Bentley, was give more to do in The Hunger Games.

Speaking of Seneca Crane, Plutarch Heavensbee is Crane's replacement as the head gamemaker for the next installment of the Hunger Games, which are a sort of all-star round of winning Tributes going head-to-head.  In the first novel, Heavensbee actually showed up very briefly when Katniss caught the attention of the distracted gamemakers with a well-placed arrow.

Hoffman joins the cast along with fellow newcomer Jena Malone, who we learned had been offered the role of former Tribute Johanna Mason last week.  Jennifer Lawrence, Josh Hutcherson, and Liam Hemsworth are all set to reprise their roles as Katniss, Peeta, and Gale for the duration of the franchise.  Supporting players such as Woody Harrelson, Elizabeth Banks, Lenny Kravitz, and Donald Sutherland are all coming back for more, too.

And for those of us who haven yet to read the novel trilogy, Lionsgate has indeed supplied an official synopsis for the sequel, which you can read below thanks to EW:

The Hunger Games: Catching Fire begins as Katniss Everdeen has returned home safe after winning the 74th Annual Hunger Games along with fellow tribute Peeta Mellark.   Winning means that they must turn around and leave their family and close friends, embarking on a “Victor’s Tour” of the districts. Along the way Katniss senses that a rebellion is simmering, but the Capitol is still very much in control as President Snow prepares the 75th Annual Hunger Games (The Quarter Quell) — a competition that could change Panem forever.

Francis Lawrence, who is taking over as director for Gary Ross, is sticking with his predecessor's attention to casting and is attracting some damn fine actors, too.  Lawrence is working on a tight schedule with a release date announced long, long before he became involved.  He apparently has a script, though, one written by Simon Beaufoy and Michael Arndt with input from Collins herself.

The Hunger Games: Catching Fire will hit theaters on November 22, 2013.