There are certainly mixed messages when it comes to Siri, which has led to debate as to whether Apple will offer it to iPhone 4 users in a future update. That possibility looks a lot less likely now.On his blog, Michael Steeber said he has been contacted by someone who had, in turn, contacted Apple with a bug report, suggesting a different build of iOS with Siri included. The voice search feature bundled in as part of a paid upgrade. Not a bad idea to be honest.Apple's reply was brief, but to the point: 'Engineering has provided the following feedback regarding this issue: Siri only works on iPhone 4S and we currently have no plans to support older devices.'That's interesting for a couple of reasons. The bottom line is that Apple isn't working on porting Siri to older phones or at least, has tried and failed. However, last week, there was a report from a 'source' claiming Apple was testing Siri on an iPhone 4, with 'special software' running on phones that include Siri already. This certainly runs counter to the new Apple statement.However, even with limited resources, Siri was ported to the iPhone 4 by developer Steven Troughton-Smith, working alongside the 9to5Mac site. It didn't work perfectly, but that was down to access to Apple's servers rather than hardware limitations. In short, Siri could work on an older phone.The reason why Siri isn't coming to the iPhone 4S is probably down to commercial, rather than technical reasons. Siri is a stand-out feature for the iPhone 4S, alongside a better camera and processor. Offer Siri to all existing iPhone users and you've just lost a considerable number of upgrades. Yes, it might well work on an iPhone 4, but even if it charged a modest fee, it wouldn't necessarily be an astute move for Apple's bank balance.