By Malathi Nayak SAN FRANCISCO (Reuters) – Video game publisher Activision Blizzard Inc, known for its Call of Duty franchise, said it raised its 2013 forecast but lowered its revenue estimates for the current quarter after warning that it could face a challenging holiday period. Despite a bump in its 2013 forecast, Activision cautioned that there is some execution risk in Q4, Benchmark Company analyst Mike Hickey said. For the fourth-quarter, which is its crucial holiday period, Activision lowered its non-GAAP revenue forecast to $2.22 billion from its prior expectation of $2.25 billion. This fell short of Wall Steets estimate of $2.29 billion, according to Thomson Reuters I/B/E/S. It also lowered its non-GAAP earnings per share to 72 cents from a previous range of 76 cents to 79 cents per share, and below Wall Streets view of 79 cents, according to Thomson Reuters I/B/E/S. The company had said last quarter that it expects a rocky holiday quarter because of heavy competition as its just-launched Call of Duty: Ghosts will battle rival Electronic Arts Incs Battlefield:4. Moroever, its Skylanders SWAP Force, a childrens fantasy-adventure game sold with actual toys that come to life onscreen is competing with Disneys Infinity, based on a similar concept.