I think @prisoner-monkeys is right here, about canopies not being the adequate solution to this accident.
Canopies do offer a solution to better protect the drivers in open wheel cars but there are some risks and disadvantages (just look at the arguments Keith posted in 2009). The FIA has been studying what effects they have because of the accidents in 2009, and in time it might be that cars will have something like that.
But if you look at the sheer force that ripped off the whole air box of Wheldons car, can we be sure even a canopy would have offered sufficient protection? What’s more important, is looking at extreme measures the best solution? In the end it only changes the danger as a results of the crash, instead of preventing this from happening in the first place.
The new Indy car chassis was develloped to limit wheels mingling and cars launching up in the air. And driver protection is a lot better as well. It might well be, that with that car Wheldon would have not been shot in the air and therefor would not have been in danger of getting into the catch fencing in the first place.
I am sure Dallara will test the new car and simulate the crash to see if it would really prevent this from happening, as it was designed to do.
But before even getting into the new car, Indy Car will have to look at the wisdom of racing on this type of oval, with a large and increasing banking. And they will have to consider how many cars to put into such a close space of 1.5 miles.
The track itself might be improved as well. At the scene of the accident it was a catch fencing with barbed wire. If you look at other parts of the track, there is mesh fencing which might not have ripped up the car as much. Not saying it should have been that way, but these are far easier measures than putting a canopy on top of the car.