the only thing about capacity that should be considered is that there won't be as much room to store assets. it suggests sony wants to move forward with more streaming solutions. it also makes me curious as to what kind of hard drive it will pack, as well as what the read speed of the BD drive will be. fast, high bandwidth ram will need to be fed assets quickly.
AFAIK, the 360's DVD drive could ramp up to higher overall read speeds, where as the BD drive in the PS3 read at a steady, albeit moderate, rate. if sony can tackle both the BD read speed and put a quality hard drive in each PS4 they could make it easier for devs to incorporate asset streaming tech developed over the last handful of years.
then the capacity difference won't matter much, to sony and/or PS4 devs.