I dont think so,even now many applications developed are tied up with IE.Take for example my Company’s aviation application is tied up tooo much towards IE (this application has been installed at PHI,CONAIR,Columbia Helicopters,ORI…these are our partial US Clients & RUAG n SWISS).No one had questioned about IE
One of the main reasons switch to Firefox is SECURITY
"IE users are switching to Firefox mainly due to security reasons as they feel that the latter is secure." –EarthTimes.org
But most of the corporate users are behind the firewall,there it is a matter of usuablity & not security.
IE will top browser market….