It does seem like the days of hiring a host who cut his teeth in radio or journalism are pretty much over. Alex Trebek's replacement will prolly have reporting chops, but comedians and actors have been the trend for about a decade now. Then again, there's also Chris Harrison, who started as a sports anchor. But, for every Chris, it kinda feels like there's 10 Billy Gardells or Wayne Bradys. Many of them do pretty well, and I'd attribute that to being able to think on their toes as comedians. Not every host works out, but I'm sure there's a newsman turned host who fizzled out as well. :-)
That being said, actors as hosts aren't necessarily a new concept, just the new normal, compared to 1975. But, back then, you still had guys like Richard Dawson and Travis's example of Chuck Woolery. I believe even Peter Marshall was an actor in commercials. Go even further back, and you could use Dick Van Dyke or Johnny Carson as examples.
I'd add Todd Newton and Mark Walberg to the new list. Great at their job, but yet to find a format that lets them shine...I'd put them in the Jim Peck category.