So what if the 8Mb pre-set limit starts to be taken advantage of? That's why pre-setting a limit so far from the original is considered radical change by many. It has never been tested in anything as large as bitcoin.
Actually it has been tested before. When 1 MB block size limit came to effect in 2010 the average block size was around 0.0003 MB. So only 0.03% of maximum block size was actually being used by blocks. With rise to 8 MB the same ratio with current usage would be 5% and situation would be relatively equal to mid 2012, when 5% of 1 MB blocks were in use.
Can you give us a good example how 8 MB limit could be taken advantage of?