My advice for those thinking of going, but yet to decide, is book a room (with 2 beds) because you can cancel it later (but check the fine-print first to see if there is a cancellation fee, as the deposit should be refundable). And book more days than you think you might need, in case your plans change when booking your flights - you can always change your reservation later to reduce the days, but if the hotel fills up, it might cost you more to add on extra days later.

Demonac and I went to San Diego in 2011, in the week before BotCon, which you can read about here.
We went to Legoland and the San Diego zoo, but there is also a Seaworld there as well, plus some cultural areas (Balboa park is one)... and for the more adventurous, Mexico is just a 20 minute drive from next year's BotCon hotel.
Plus, if you are flying in through Los Angeles (as most flights from Australia do), you have a whole heap of things to do there as well, including the Transformers Ride at Universal Studios.

Next year is one of the cheaper options for Australian fans, as it is on the west coast of America (less flying), so I'd imagine a few people might go... but the hype for the "official" convention is a lot less than it was 4-5 years ago, which makes it harder to draw in long-distant attendees.