Just like they haven't specifically stated how long the flight restriction will be in place, they also haven't specifically said that flying in the older content would remain.
Also, i'm not sure how it is for you, but the last time i was on a flying mount, i was still able to see the world around me and it didn't detract from seeing the beauty of the world below me. In fact, it gave me a different perspective than on the ground seeing everything. Why do you think the Space Needle in Seattle is so popular? I mean, the people of Seattle (and tourists) can easily just see things from the ground, right? Oh, that's right, people like to have a different vantage point from time to time. Besides, as has been said MANY many times, even if flying is in the game, nothing is forcing you onto a flying mount if you would prefer a ground mount to travel.
Flying should be handled as it has been in the past: locked until level cap is reached.