Well, the premise of the show that they went with (Lost ship, survival stuff) was only good for 1-2 seasons anyways. Scorpion might be a good way to end the series, with them using Borg tech for a one-way trip home (it all blows out after one usage).
^ That's an interesting idea but I found that I wanted to continue the series because Scorpion was so good. It would have been a shame to end the series right when it became interesting. Nemesis is my least favourite episode of the series. I'd rather watch Threshold.