Regardless of the moral and fan boy arguments it did seem to me that TWOK inspired 'Nemesis' was leaving the door open for Data to return if there was another sequel. Anyone disagree with that? Some cast and crew interviews suggest that also.
Yes and no. The thing to remember is that there are different people and groups involved in making a movie, and so there can be more than one intent or purpose shaping its content. It was the
studio's intent to include a back door so they could bring back Data if the movie was a hit and audiences clamored for Spiner's return. But that wasn't the intent of the people who came up with the story and script. Spiner wanted to kill off Data because he was getting too old to plausibly continue the role.
His intention and his collaborators' intention was that it would be the end for Data, period. Within the context of the film as written, B-4's little song at the end is just Data's legacy, a ray of hope that B-4 can learn and grow after all thanks to what Data left him. Of course it has the
secondary, backup purpose of being a potential back door for returning Data if that became an option. But that was a contingency plan, not the primary purpose of the plot development.
You see this a lot in fiction, especially collaborative fiction. A story is told with a certain primary goal in mind, but with just a bit of a hedge thrown in
just in case future creators or changing circumstances lead to a change of goals. That doesn't mean, however, that the hedge represents the creators' original or primary intent. It's just a backup plan.
For instance, in
DTI: Watching the Clock, I established a lot about the future of the Federation -- but I made sure to include a line hinting that maybe the future glimpsed there isn't
the future, that there's a chance the whole thing could've been changed. That doesn't mean I intended that whole future to be non-binding; it just means that, whatever my own intentions, I recognize that I'm not the one in charge of the franchise and I have to leave some wiggle room in case other creators decided to take the continuity in an incompatible direction. If you're part of a collaborative creation, it's just good sense to leave in that kind of wiggle room -- not because you want or intend your decisions to be undone, but because you're aware that
someone else may decide to undo them.