I really wanted to go for the Fenrir mount. I find the triple triad game pretty entertaining so I don't mind grinding the MGP. Do you think SE will keep current mounts useful in the expansion? Or will they just be trophy pieces that become obsolete due to the flying mounts?
They'll all be useful since flying from what we've seen and heard so far isn't going to be the "go to" for general travel since largely it's only the floating areas that uses them heavily and while they're slightly faster than mount running, there aren't only flying areas coming. There's still going to be plenty of areas where you're on foot. Fenrir for example already is a trophy mount when you get down to it.
In the last live letter, it was acknowledged that Flying mounts have roughly 80% (tentative number) land speed as the land mounts, and flying mounts cannot fly in most ARR zones.