You do not need an exact date to start budgeting and planning.  How is this any different than when the park is building a new ride or attraction, and you want to wait util it opens to visit?  you plan accordingly.  Will you be the first one there, well unless you are a local or can travel at the drop of the time when dates and times are dropped then no.  If we get an opening date 3-6 months before the park officially opens, that is plenty of time to plan and start planning a trip to a park that will not be closing anytime soon.  I seriously doubt anything will be going on sale this year unless the park plans on opening in March or April.