The official reason is that the landowners are 'resting the land' for a year.
The whispers in the business, however, are that the organisers have a few problems that they want to address. Security and general organisational problems, although already addressed to some extent, need further consideration. There's also the matter of cost. Although the festival claims to make money every year, the costs of staging it are huge and there's a worry that they may not be able to afford it for much longer.
There's also the fact its 'grandson' is giving it a little too much competition -
http://www.summersundae.com/ - sorry, that was a shameless plug, I know, but hey, it's gonna be a good 'un.