Yeah the waiting game with cars is a tough one.
I have enough trouble as is using all the power the 335 has on a daily basis. Even when I want to drive fast I find that 6th/7th gear and under 4000 RPM has more power than I'd ever need since the torque curve is so damn flat.
So would I wait for marginally more power, probably not. I contemplated waiting for the new navigation but I'm glad I didn't, my life is just fine without it.
2013 335i M Sport /// Alpine White/Coral Red