They were CONSIDERING it in the leading leading up to the release of ANH. Lucas's story ideas became too big for one movie. So they made a part of it: ANH. If it were a success, maybe the rest of the story idea could be developed into more movies: nine or even twelve. In talks producer Gary Kurtz suggested nine or even twelve movies with a rather elaborate story in whoch Leia was never Luke's sister, but that Luke would in fact go in search of his sister and in episode nine or twelve Luke would finally confront the Emperor (after disposiong of Vader in epVI). But there were mere story ideas. With ROTJ Lucas decided to abandon those pretty good ideas and cramp the whole lot in one movie (hence the sloppy Luke-Leia bond and Solo surviving and becomeing a happy couple with Leia).
So... they never PROMISED you anything. Obviously Lucas was done with SW when ROTJ came about, feeling limited bij the technical impossibilities. When Jurassic Park came around he saw a chance to do Ep I-III and that was it.
It does actually. because when Lucas saw what Spielberg had done to Jurassic Park he suddenly realised this was the technology he had dreamed of when making the OT. He stopped making Sw because he was disappointed with what he could make. Seeing JP, he realised there's a new possibility to revive the franchise in the way he originally envisioned it.
So first he started making the SW SE's to see if it could be done properly. Being satisfied with that he proceeded with the PT.
But that's more a design choice, not so much the quality of the CGI. I think that had to do with advanced understanding of what raptors looked like: colour and the possibility of feathers.
Registered: Jun 2006
Location: The United American Empire
It is different than the first movie's island. (Isla Nublar.) They are on Isla Sorna in the second and third movies, the Raptors on Isla Nublar and Isla Sorna look the same in the first two films. So unfortunately you can't use that bent excuse.