If you are in business as a wedding photographer the only thing that matters is what actually sells. It doesn't matter fad/no fad or what style you have if you can't sell it. As a business you should follow your bottom line.
I'm not sure that's the best advice. For someone starting out, I'd say it's bad advice, with respect. Often, what sells isn't great - it's popular in the short term, but may bury you in competition in the long term. It's like the ice-cream seller at the beach selling vanilla cones because they're the most popular, but failing to take into account the twenty other guys doing the exact same thing right next to him. If he sold strawberry cones, they might be less popular, but he's cornering the market because no-one else is pushing them. He wins.
Of course, if you're selling the prettiest vanilla cones at the same price as the competitors, you might have the edge, but still...
I think these days, with the photographic market getting increasingly saturated by people selling vanilla photos, you need to develop a point of difference. And you can develop a POD without shooting images that will become dated. I genuinely think that a good photo - something with emotion, creativity, and uniqueness - will stand the test of time.
Also, thinking about your bottom line should come late in the game, not early - or not at all. It might sound cliched, but those people who do it for love tend to do it best. And like any other industry, I think you need to do any jobs you can get your hands on at first (and I'm talking several years), to learn and develop a portfolio - without thinking about $.