If it's a one shot, why give it a cliffhanger ending? Cliffhanger endings usually are for stories you intend to do a next part to.
I guess for me it's all in the word used- one shot. For me a one shot story is gonna have a beginning & end and the creator has no intentions of making a sequel or next part.
Read this thread a little more, and I agree- an open ending would sound more like what you need. Maybe something along the lines of you wrapping up your initial story, and having the characters to decide to embark on another journey/mission/whatever, having the story to end right there. Ending the story at the start of a fight and leaving your readers hanging(especially if for years) could irritate them into not wanting to [continue] read your future works