1) yes true, but it will become less and less overkill as the new games come out.
2) you should be fine for the next 3-4 years i would guess, unless vista and DX10 does something terrible to games. i play at 1600*1050 everything on full with all games just fine with my 7800GTX
3) yes the processor will bottleneck you, but if you crank up AA and AF the processor will become less of a bottleneck since the Graphics card will be doing the work.
btw i wouldnt of said that pentium D was comparable to the e6400, but it doesnt really matter too much for gaming.
take a look:http://tomshardware.co.uk/cpu/charts.html?modelx=33&model1=433&model2=438&chart=173