The problem with giving specific deadlines is the fact that they cause problems for development and PR/Marketing departments. If you set the deadline too soon, you risk having major issues to fix at launch....which cause a PR nightmare. If you set the deadline too far out, Marketing has to fight that challenge as well as simply trying to figure out how to sell a product. There's also the risk of missing the deadline due to unforeseen problems....
Personally, if I'm looking to buy a product now, but it's manufacturer tells me it's going to get a major software upgrade 6 months from now, I'm going to assume the product is defective already. Or I'll simply have flashbacks to my HTC Trophy and the empty promise from MS that every phone would get 1 major OS version upgrade in it's life span....which turned out to be a lie from day 1.... Now I'm hearing rumors that my HTC Trophy might not even get WP7.8...