I think user *Megs* summed up last night's Kyle XY series finale best by coining it: "one of the most F-ed up series finales I have ever seen".
Why the huge cliffhanger? By the time the Kyle XY producers learned of the show's cancellation, it was too late to film a proper finale. In fact, the show had already finished filming its season!
BTW...if you want to throw your anger in another direction, try The Secret Life of The American Teenager. It was this show's huge success combined with deteriorating ratings for Kyle that led to its ultimate doom.
At any rate, since any kind of additional resolution is highly unlikely, check out this interview on ABC Family's website with one of the show's writers answering some additional questions about the finale and in what direction the series might have been headed:
Amanda or Jessi? - The "who will Kyle end up with" question is a question we have a hard time answering, because in our opinion a true hero is often destined to end up alone. Had this show run for five more years, Kyle would have likely ended up with neither, knowing that he couldn't fulfill his true destiny as a prophet by living a normal relationship life like everyone else. But in the short-term, we absolutely believed that Kyle and Jessi's relationship would have continued to develop.
Cassidy is who? - Cassidy and Kyle share the same genetic mother. Cassidy wasn't lying. No one else is related (as far as I know). The David and Goliath relationship between Cassidy and Kyle would have been a large part of next season.
Read the full interview: