I think that the effect of the switch to 75kWh battery is not in increase of the sales, but increase of the gross margin on the low end by at least 2%. (consider $3K price increase vs. 5kWh X $190/kWh = $950 cost). This can't possibly be a bad piece of news...
Looks like from this thread that 75 kwh is already built in to 70kwh Model S's, upgradeable by firmware upgrade for $3250. That would indeed increase their GM.
Slipping Delivery Dates for Model S