If the M4 is anything like what the F10 M5 did to the E60 M5, it would utterly destroy the E92 in every way possible. At the same time, the V10/V8 twins born from the BMW Sauber F1 legacy would live on as probably the golden age of M naturally aspirated motors. No new M cars will ever feel/sound just like it.
No offense, but I find the new M5 pretty sedate. Its devastatingly fast but as an experience, it doesn't floor me quite like an E60 M5 or the V10 M6. I am guessing the same will happen to the M4.