[UPDATE: Deadline's source are reporting that Ross has not yet "formally withdrawn" from Catching Fire. The filmmaker is currently on vacation, so there presumably won't be an official confirmation either way until he returns to work.]
Truth be told, Lionsgate had already taken precautions for an event like this. The studio recruited Oscar-winning screenwriter Simon Beaufoy (of Slumdog Millionaire and 127 Hours fame) to start working on the Catching Fire script, back when Ross was still busy working the promotional circuit for Hunger Games. Hence, the ball’s already off and rolling on this tentpole production.
Couple that with Fox’s newly announced 2013 start date for filming on X-Men: First Class 2 - which will free up Jennifer Lawrence to reprise her role as Katniss Everdeen in Catching Fire this fall – and (for now) it doesn’t appear that Ross leaving the Hunger Games sequel will trip up the film too much on its way down the production pipeline.
Fan reaction to the news concerning Ross’ vacating the director’s chair on Catching Fire will probably be somewhat mixed, as far the immediate response goes. On the one hand, most people seem to agree that he did an admirable job of translating Suzanne Collins’ popular dystopian sci-fi thriller into cinematic form; on the other hand, some of Ross’ stylistic choices with Hunger Games (specifically, the disorienting shaky cam/editing approach) left many viewers feeling disgruntled.