I think the F30 will be quite smaller than the E39 in terms of overall exterior length.
My quick research showed the following inches (rounded):
The E34 was 186 and E36 was 175.
The E39 was 188 and E46 was 176.
The E60 was 191 and E90 was 178.
The F10 is 193.
If the past can be a predicator of the future, I assume the F30 will be 180.
'09 MB E350 4Matic
Missing my '02 325xi w/ manual trans
one good site: www.realoem.com