I don't think that design trends changing necessarily make certain tattoos a bad idea to get though. You could probably say the same thing about the classic American style (though it's persisted in popularity for a long time). I think it's all up to what you like personally.
This is a design that I sketched up a little while ago, and I'll probably get something like it eventually (ignore the straight lines and scribbles on the outside). Not sure where yet though. It does incorporate things that have meaning to me: the sun image & its radiance, the flower (horticulture/gardening/connection with the natural world), and definitely some stuff that is trendy, particularly the lotus flower/mandala image. I just genuinely like how it looks, the organic lines. Still gonna sit on it for a while though and modify it.
The thing about how the body will change over time is really interesting. I wonder if I could figure out a design that would look better with wrinkles (lol). That's a neat idea to play with.