Sonia Rykiel is in her seventies and designs beautiful clothing. Sonia has a way with knits. Not all of her clothing is for an older customer, but there are some re-interpretations of classic suitings. This is her fall 2007 collection. Link
Women over forty, fifty, and sixty are facing some fashion problems as many designers are aiming at a younger market, and much of the clothing is not designed for an older women. Although today's woman, forty and beyond, is fit, style conscious and looks fantastic in fashionable clothes, in many cases the marketplace has forgotten her.
Here is an article: Older, Better, But Harder To Dress -
"AT the start of any fashion writer’s career there is, waiting at the end, the dreaded article about older women and how they can never find clothes appropriate for their age. I swore on a stack of Vogues I would never write such a piece. It was totem journalism, predictable, worked at. Even the term “appropriate” has always seemed to me old hat, with violets on top." NY TImes