Sure, rose gold is a trend, but it's been around now for quite a while and I think that it will be around for a while. I would be concerned about quality issues because I'm not so sure that MK watches are a good investment for everyday use (unless you purchase a SS version). Personally, if I was purchasing a watch for every day wear, I wouldn't consider MK. MK yellow and rose gold watches are plated and the gold color (yellow or rose) will fade. Having said that, I'd be willing to bet that the rose gold plating on a MK rose gold watch would last at least as long as the rose gold trend, so you likely wouldn't have to worry about your watch going out of style (in other words, your rose gold watch will wear out before the rose gold trend wears out).
Here's an interesting thread that might be worth reading:
how to care for new michael kors watch?