I believe the Spark is the most important drone in DJI's line-up. No Spark and your entry price is $799 or higher, that is a rather steep price for anyone to pay for your first drone. If DJI hopes to sell tons more drones, they have to entice new drone flyers with an affordable, yet capable model that will fully satisfy some and whet the whistle of others leading to more drone sales.
I chose the Mavic Air because of the neat features and the fact that I can afford it. However, my current needs can be totally satisfied by the Spark. 1) Extremely portable 2) great 1080 footage - don't have a computer that can edit 4K 3) Easy to fly (will be my first drone) 4) flight time and distance no problem since I'm mainly using it for family outings, vacations and other functions and just having fun flying 5) and great entry price.
The Air does not obsolete the Spark in the least, it just gives many more people a more affordable upgrade path. And for you more demanding droners the MP 2 will no doubt satisfy the vast majority of you.
Also, I will likely give several Sparks as Christmas gifts to some lucky nieces and nephews because it is a quality drone at a great entry level price.