His track record is the one thing that makes me think that he can pull this off. Even his ventures that were not as hugely popular still did well - The Abyss is one that comes to mind, as does True Lies. What would really help his case for success is if he has someone (or several someones) help him write the story/dialogue of the sequels.
The one other thing that wouldn't surprise me is that since he now has a partnership with Disney, expect to see way more in the line of merchandise from these movies. One of the critiques I often see are "yeah the land will look beautiful in DAK, but what will the merchandise be like?" I think that could change in a big way now that he is working with the marketing/merchandising giant that is Disney.
Cameron has never really repeated himself in a big way, has he? Seems like he's thrived on change and variety, at least in the sci fi action/romance genre.
Maybe he's thinking of outsourcing the four films and just using the money to fund other, original projects.
My husband and I were just talking about this today. Seriously according to wikipedia (yeah yeah maybe not the best source) the last sequel shows coming out in 2023 a full 14 years after the 1st. I have no idea how successful the sequels will be throughout the world but still the 1st is coming out 9 years after the 1st 2018 with the others sequels coming out (according to wikipedia...again yeah on the source) in 2020, 2022 and 2023.....though the dates are pretty far out at this point. IDK I may get more excited towards when the 2018 sequel comes out and see if I will want to invest in going to the other 3.
I wonder if it will become a Christmas tradition to get a new SW Episode on each odd year and a new Avatar film on each even year (except for 2023). Disney will probably move IX to Christmas of 2019. This does create a question. Can Disney move their Star Wars Story films to those time slots and compete with Avatar?