here are two popular Asian realms:
http://www.wowprogress.com/pve/tw/crystalpine-stinger
http://www.wowprogress.com/pve/kr/azshara
Almost 95% of top 100 guilds are dedicated 10man (not 10/25 as you mention, check second and third pages also). So I think 10man will stay 10man even if 25man drops that much better gear. Its like 95% of raiders here cba doing hard modes even though gear there is much better there. 25 man is harder in its organization ways so 10man will stick to 10man (probably) and 25man guilds will have a reason to go on and survive.
** Edit: Although all these things are just based on what I see there, was sort of surprised to see it myself. Not sure if same will happen here or not.