BRG have discovered iPhone firmware 3.1.3 and firmware 4.0 by analyzing their sever logs. The existence of iPhone firmware 3.1.3 and OS 4.0 is very much clear from the server logs. No one is sure about what new features iPhone firmware 3.1.3 will offer but most probably firmware 3.1.3 will be a minor release for patches and bugs where as iPhone firmware 4.0 will be a major release and is expected to be released in the summer of year 2010 with the next generation iPhone 4G.
No one knows when iPhone firmware 3.1.2 will hit your iTunes but if you are on jailbroken / unlocked iPhone firmware 3.1.2 then DO NOT upgrade to firmware 3.1.3. You may loose the capability to jailbreak or unlock your iPhone forever. As far as the legitimation of the server logs are concerned, even if they are not true but one thing is for sure that Apple is working on something new. The competition in year 2010 will be tougher than ever as Google Phone Nexus one and new Driod both are scheduled to be released in year 2010.