"Can"? I'm sure they "can". The word we're looking for here is "won't". At least not yet.
They plan marketing around what their analysts will maximize the effect. If anybody thinks there are swathes of people who will buy DDN if they announce the date now, but won't buy DDN if they announce that same date next month, they're kidding themselves.
I wish I could be as confident as you that it is "won't ", but recent comments have the
game sounding unfinished.
I agree that an announcement date of now or a month from now won't have any
big impact on most (I've done all the open play testing, like what I've seen, and will
be purchasing as soon as it is for sale). My fear is if they don't have it out for Gencon
then they miss the marketing opportunity to pitch to pathfinder/3.x/lapsed players, etc.
Getting those folks to try it during the excitement and energy of the con....after which
they may go home to pitch to their friends..... Well that would be a marketing failure
of legendary proportions.
Further as to marketing, my opinion of WotC marketing (in regards to D&D)
for quite some time, with a couple of exceptions, is that it ranges from mediocre
to lousy....unfortunate since I'd love to see D&D do well.