I actually don't see the point in adding flying to old areas if you're not going to do anything with it... Getting the increased speed would be nice, but old zones are relatively small and have no real need for a speed boost...

I'd still like them to add flying to old zones, but not as just a "Fine, here you go" sort of way, in a way that actually provides something new to the old zones. Take Southern Thanalan, rather than just adding flying to the area, I'd say add new areas to the area that make use of flying. There is that big old tower in the distance for example... So rather than it just being a case of "Here's the old zone, now you can fly in it", it's a case of "Here's the old zone, now you can fly in it and discover new areas!".