It's bothering me that you are predicting delays already. I would be more interested if you could set dates you feel you can realistically meet, rather than posting dates and expecting delays.
Development processes are subject to reiteration, as usually new questions arise through every stage of the project, especially if it contains new technologies.
We have a plan and feel the set dates are realistic, but we also know from experience where roadblocks tend to materialize unexpected. As we don't want to work on the basis of "worst case possible" (which may still be delayed anyway), a combination of timeframes and possible delays seems the most sincere approach.
If you look at other large projects, you will usually find delays without announcement.