1) a decrease in freep players overall (less $$$$ for Turbine); 2) a huge shift in the classes you see in the pvp zones; or 3) a significant swing of the ratio of freeps:creeps.
I wouldn't mind seeing a few less freeps out there on Arkenstone atm. Either that or I wish they'd move into smaller groups to decrease some of the lag.
Already happened. In the last 2 weeks we've seen an increase of Minstrels and Loremasters. That may just be the influx of new servers but it's also likely folks are playing these characters because they're so powerful atm.
Ratio of freeps to creeps - for Creeps to break even in a fight it's generally 1 freep per 2 creeps. For each minstrel it increases exponentially, with 17.1 a defiler can negate ~1/2 of a minstrel's increase.