So, just as a reference here are the keys we're currently seeing as ones that will not be converted to gold or removed upon release of the patch -- if you have them they'd be put back into your normal inventory. This isn't necessarily a final list, and it's possible we could cut the list down even further before 4.2 releases.
Ключ "Угрюмого обжоры" (BRD)
Secret Safe Key (BRD)
Ключ темного хранителя (BRD)
Ключ от древнего сундука (BRD)
Jump-a-Tron 4000 Key (Nagrand)
Колкарский трофейный ключ (Barrens quest)
Ключ от тюрьмы братства Эфириум (Netherstorm – Blade’s Edge)
Ключ капитана (Tanaris)
Any Blacksmith keys (e.g. Titanium Skeleton Key)