Confirming here too, the correct avatar shows only on my profile and posts. At the top of the website and in-game one of my really old avatars shows for some reason.
(currently testing with outdated couple avatar pic)
EDIT: i think the uploaded avatar gives new filename instead replacing the old avatar that stored in bancho, i don't know since when this is changed, but i'm still remember that when someone pointing to other always uses avatar instead name only.
I have had my pink kitty for the past year since last Christmas. The one showing up beside my Welcome is the one from before last Christmas. I have not changed anything at all since last year. Avatar showing up beside my Welcome is also the one showing up on my osu! client.
Conclusion: avatar that loaded into game and shows beside your name in web is directed to http://osu.ppy.sh/a/ while your avatar on forum is loaded from http://s.ppy.sh/a/