Any Lunacon regular here also a member of Worldcon? If you're attending, then you can do site selection at the con, but if you won't be there, site selection by mail or email must be done by tomorrow, the 10th of August. Details can be found here.
The basic rundown is that it's a four-way battle between Helsinki, Washington DC, Montreal, and Japan. Japan's a crazy long shot, as they have the spectre of insolvency hanging about them -- it is said that now, eight years in, they haven't paid all their bills from the last Worldcon they hosted -- so it's highly unlikely that they'll win. Montreal is said to be less likely to win, though if it did make it through the six hour from from Westchester would make it a value proposition for folks in the Lunacon area.
Otherwise, at a little over four hours away by car, Washington DC is the most drivable pick for folks who go to Lunacon. I know Lunarians and Lunacon regulars who couldn't possibly afford a Worldcon unless it were this close, so this is definitely an option to pick if you'd like as many familiar faces as possible at your 2017 Worldcon or if you yourself can't put together the budget for an airplane trip across eight time zones. They'll also have a more familiar structure than an overseas con would. European con parties, for instance, often take place in a convention center with segregated spaces and sometimes mandatory catering and other things US-based congoers may not be used to.
Helsinki is the "keep the World in Worldcon" option, and they have a mission statement of using Worldcon to help unify European fandom. All of continental Europe has only seen two Worldcons in history, whereas Montreal and nearby Toronto together have seen four -- the most recently only six years ago -- and the area of DC with nearby Baltimore and Philadelphia have colllectively seen seven Worldcons! This is definitely the one to pick if you'd like to see how distant fen throw a con, and if you'd like to get some good sightseeing in (because, let's face it, if you're in New York, chances are you've seen a good chunk of DC already in your lifetime!).
So, there you go... a quick reminder as well as (for non Worldcon members) informing that there might be a World Science Fiction Convention in drivable distance in 2017. And you should really save up for a trip to New Zealand in 2020, if you can -- that one should prove to be magical. :)
More info on future Worldcon bids can be found at http://worldcon.org/bids/
(Disclaimer: I'm voting Helsinki, as they are total pussycats and have thrown what is in my opinion by far the best of the bid parties, but I won't complain if I could drive all my gear to a Worldcon Hotel two years from now!)