I totally see why TSL would beet Avatar. The target Disney audience is families with kids. Their kids love toy story and love TSM when they visit DHS. So they know they will just "love" this new expansion. Most families with kids are not going to be more excited about Avatar. Where I think AK will make the most impact is now being a full day park with things offered in the night. I think it will force people to stay longer in AK and potentially add a day to their vacation. The other option is the remove DHS and replace with AK, but that only lasts until TSL opens up in 2018. Then people add a day to their vacation.
I think a small group of people will plan additional vacations around this, but I think more what will happen is how people vacation at the 4 parks will change with AK taking up a larger chunk of time in their vacation. When DHS gets TSL & SWL it will also change things because DHS will be longer, but I personally think they need another phase for that park to even be considered a full day park. I think because of waits and new offerings it will be a full day park the first year SWL opens, but will quickly drop back down to not a full day park.