Is Prometheus Really Part of a Trilogy

I was thinking about this question today as debates about profitability and sequels raged over the internet as the weekend box office numbers started trickling in. The sequel talk got me reading articles and interviews and it dawned on me that Lindelof has said that he would be "open" to coming onboard and writing a sequel if he was asked. This very likely means, that the rest of the Prometheus story and, many of the plot elements left open, have not been written out yet. This puts Prometheus more into the category of standalone film with sequel potential (like Batman Begins) than the first part of a trilogy. I think this may be the thing that is confusing audiences the most about the story. It has been marketed and talked about as a standalone film with the potential for sequels and yet is clearly a film that REQUIRES a sequel to complete the story. Do you guys think that maybe if they had marketed the film as the first part of a trilogy from the start that the reception for the film may have been significantly better? I personally think that if the studio had committed to two other films from the beginning the film's rating might be in the low 90's or high 80's and the box office would be much larger. As of right now though, it seems the two other films have not been written and no director or writer for a sequel has even been hired. So as far as the general public is concerned, this is an incomplete standalone film.