Many organizations have common characteristics in this regard. First, they don't expect you to be on time. Sales may think you're going to launch on time, but it's in their financial interest to think so. The rest of the org probably made a schedule they know you can't meet because they think it motivates you to work harder.
Second, unless you're in a startup where everyone's inexperienced, most people probably already know you'll be late, but aren't saying it out loud. They likely have discussed it (up the chain) in meetings you're not in.
Third, people do shoot the bearer of bad news. You can earn a rep as a negative person if you make _true_ predictions out-loud that don't fit the common desire. This is especially true if some of the senior people who know (like your boss) haven't been forthcoming with their bosses.
Have a quiet conversation with your boss over lunch or beers - not a meeting - and tell him/her what you think. Be prepared with details, but if he/she doesn't ask for them, don't provide any. There's a good chance he/she already knows as you suspect.
Even more casually (lunch/beers), express your concerns to the project owner. It's probably not new news to him/her either. Being "positive" is a huge part of the corporate game.: Again, if no details are asked for, don't provide any. Shift the conversation to the weather or the world cup.
You're now down. Go back to work.