Reader Morgan Berry asked me about this one awhile back, and it was amazing how much research he put into it! He found quite a few references to the series, and he was mostly curious what the deal was with the series - why was it canceled? Was it ever produced at all?
All fine questions.
Sadly (well, maybe not sadly - SORTA sadly), the answer to the question is a fairly mundane one.
Longshot was a Marvel mini-series from the mid-80s that launched the comic careers of both writer Ann Nocenti (she had worked in editorial, but this was her big break, writing-wise) and Art Adams, who was not even 20 years old when he drew Longshot!!
While a critical success and having a cult following (and certainly making Adams one of the most popular artists at Marvel), Longshot was not a huge commercial success. In fact, the original mini-series was intended to be an ongoing, but was changed to a mini-series after the series began!
While sales was a major factor, the slowness of Art Adams was a factor, as well. He has always been a very deliberate artist, and takes a long time to finish his work. The six issues of Longshot took, I believe, about two years to draw.
After the original mini-series ended, Nocenti and Adams were going to re-unite for a follow-up to the first mini-series.
However, and here is where the answer is a bit mundane, other stuff just got in the way - mainly that Adams was so popular that Marvel wanted him to do more work. And because he was so deliberate, Marvel preferred that he spend his time on more high-profile work rather than Longshot, so by the time he finished these other projects (mostly X-Men Annuals with Chris Claremont) far too much time had passed, and the project was dead. It was not like Nocenti was waiting for Longshot, either - she had moved on, as well, with both comic book work (a long run on Daredevil) and writing work outside of comics.
So I'm sorry, Morgan, all that time and the answer is pretty boring!