It appears from the video that all the models of the basic faction mounts will be updated with patch 5.1, with these new models replacing the basic wyvern and gryphon, the swift wyvern and gryphon. There is also a new mount variety being introduced: the Grand Armored Gryphon and the Grand Armored Wyvern. These are the heavily armored models in the video, and require artisan riding.
Inevitably, there will be players who prefer the old models, so it will be interesting to see if they are just replaced, or kept around somehow for those players' delectation. It's really exciting to see that Blizzard is working on these models, as it bodes well for other model updates including, if we dare to dream it, character models!
Of course, character models, with the vast variety of animations and clothing and the like will take far longer to complete than a few wyverns and gryphons. But nonetheless, any model updates are usually welcome!
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