Sony CEO Kazuo Hirai said in the business section of The Times,"Why go first, when your competitors can look at your specifications and come up with something better?"
Nintendo has already released their next-generation system, the Wii U, so it brings to question if Sony will be able to hold out for Microsoft's announcement as they plan. It seems highly unlikely that his comment about releasing a stronger system can be 100% true, since it would likely be too late to drastically improve system specs at this point in the development cycle. It seems more likely that they would simply want more time to change their marketing strategy when it comes to advertising for the system.
Sony also announced earlier in the week that they may plan to retire their long serving Dual Shock controller.