No spoilers in the OP, other than that the endings are cliffhangers; but I suspect spoilers will be posted.
In another thread, VC03 describes the ending of the second season of Twin Peaks as ‘the mother of all cliffhangers’. I really wished for one more season.
What other series or films ended with a cliffhanger that was never resolved? For me the MOAC is at the end of Riget II (AKA The Kingdom II).
Galaxy Quest (the TV series).
Not resolved in the original series: Alien Nation, though a movie was made later that resolved it.
The Italian Job (1969)
Ha! I love that film! 
WKRP in Cincinnati ended on a cliffhanger, suggesting Travis had made some kind of deal with Mama Carlson. Though there was a short-lived New WKRP series years later that was about one billionth as good, I don’t recall this issue being clarified.
And you left it out of the OP? C’mon, is there a bigger cliffhanger than this?
Here’s an earlier thread on series with disappointing endings, many of which are unresolved cliffhangers.