Here is what the analysts at Wedbush Morgans said

“We expect Sony to defer a decision regarding PS3 launch until it is able to assess the likely success of the Xbox 360, and anticipate that Sony will make its decision shortly after the Xbox 360 launch. We do not expect the PS3 until mid 2006, at the earliest, and should Microsoft fail to garner sufficient software support to gain an insurmountable lead, we think that there is a possibility that the PS3 launch will slip into early 2007.”

Again this is highly unlikely both because there are no indications to that the Xbox 360 will fail, and because it would be a very strange strategy for Sony to just sit and wait for the Xbox 360 sales numbers to come in before they plan their own launch.