In vanilla Ironforge was the main capital city for the alliance because it was the first alliance city with an auction house and it had a central location on Eastern Kingdoms. In TBC we moved to Shattrath, in WoTlk to Dalaran and in Cata to Stormwind and we never moved back to good old Ironforge.
In Classic all cities will have an auction house, Ironforge will still have a better geographical position in classic but players have been used to Stormwind as main capital for so many years now.
Will Ironforge remain the classic alliance main capital city or will it swift to Stormwind because people have get used to it over the years, what do you think?