That depends. If there are 7 million of - for example - a particular brand of washing machine and 1 million of them burst into flames, that obviously makes the remaining 6 million rather less valuable. (Also, most of the bitcoins lost so far have been stolen rather than destroyed, so the number in circulation hasn't decreased that much.) On the one hand you have the decrease in supply, and on the other loss in confidence in Bitcoins as a result of the heists.
Actually, I'd say the number in circulation has likely increased rather dramatically as a result of the heists. Consider that the thefts were from people hoarding bitcoin and the thieves are likely trying to circulate them and cash them out as soon as possible.