Wall Street’s biggest believer in an Apple TV set is losing his faith

"Each month that passes," writes Piper Jaffray's Gene Munster, "reduces our confidence."

FORTUNE -- Pity Gene Munster.

It's been five years since Piper Jaffray's chief Apple (AAPL) watcher first alerted investors that Steve Jobs' "hobby" -- the Apple TV set-top box that launched in 2007 -- was merely a precursor to a more ambitious project: a full-blown Apple television set.

"While Apple downplays...