I considered the new M5 as a one car solution, as opposed to my current two car situation. However, the new M5 fails big-time in one crucial area. BMW M cars are special because they provide world-class sports car dynamics, yet are practical and refined enough to be daily drivers. The new M5 has a fuel range of (per Road and Track's tests) of 180 miles!
The new M3's will be about the same because while it will get slightly better gas mileage, the fuel capacity is less. A fuel range of less than 200 miles is acceptable in a Ferrari which is used primarily on the weekends, but as a daily driver this was a dealbreaker for me.