The 928 is indeed the Porsche flagship that never replaced the 911. The 928, 959, Carrera GT, 918, and only the most recent GT3 models have a double wishbone; all the SUV and sedans Porsche has made have double wishbones. A double wishbone suspension is extremely important. As it allows you to maximize your tire surface on corners where the road is cambered not in your favor. The Porsche 911/Boxster/Cayman is the only very expensive car in the world that I can think of that is on a MacPherson Strut suspension (true, you can get a BMW M3 priced to the level of a Cayman, so a few exceptions exist). MacPherson struts were taken from the original VW Beetle design and adapted to the 911 design. In both the Beetle's case and the 911's case, a MacPherson strut was chosen to preserve space in the smallish front trunk of both cars and to reduce costs. Also, because West German roads were built well and windy roads were always properly banked in West Germany, a suspension system that could handle both correctly banked and incorrectly banked corners was not a priority - considering it would likely cost front trunk space.
However, you will note, no current Ferrari, Lamborghini, Bentley, McLaren, Rolls Royce, Aston Martin, or any other expensive car uses a MacPherson strut - all use double wishbone. As there are significant performance drawbacks to MacPherson struts. Even Mazda Miata, Alfa Romeo 4C, and the Alpine have double wishbone suspensions!