In a Reddit AMA Assassin's Creed 4: Black Flag lead writer Darby McDevitt has said that it's unlikely Ubisoft will use Assassin's Creed 3 protagonist Connor again in future games and also ruled out an entry in the series set during modern times.
Speaking about whether there was a possibility the series would return to Connor he said:
“Not at this time. Embers took [six] months to make. It was a big project, and beloved by all, but those teams are busy with other things right now. But we loved the project, so maybe we'll go that route again one day.”
McDevitt added that it was “not very” likely that Connor’s story will be expanded upon in another game in the future. He also ruled out a contemporary setting for a future title commenting:
“I doubt we would do a modern day AC. There are just too many mechanics we would have to develop to make it [believable] … vehicles, plausible modern cities, a huge array of ranged weapons, etc.”
“The modern day will most likely remain as a ‘context’ for all future games, something to tie them all together. Watch_Dogs will scratch the itch for a modern day AC. Just wait!"
McDevitt also said that it's unlikely Ubisoft will resolve the Assassin Templar conflict.
“As for the Assassin Templar storyline resolving. I don't think so. [It’s] been going for 80,000 years already. Why stop it now?”
“There will certainly be a resolution to the most recent plot developments, but the overall conflict will probably rage forever, just like most deeply divided philosophical conflicts."
He believes that if each new Assassin’s Creed game adds “unique gameplay innovation to accompany its setting” and the present day element is refined “to be more of a ‘context’ and less ‘plot driven’ so that people aren’t constantly frustrated by a lack of resolution” than the franchise could last “quite a long time.”
Despite McDevitt's comments Assassin's Creed 4 director Ashraf Ismail has said that "there is an end" to the franchise which Ubisoft will use eventually but when that is will most likely depend on how long the series remain successful.
Ismail also revealed that developing Black Flag for current-gen systems was "nightmarish" but PS4 and Xbox One production was "smooth".