Microsoft officials announced on January 18 that this will not be the case.
After January 31, the $39.99 upgrade price will end. Starting February 1, the Windows 8 upgrade (from previous Windows home/consumer SKUs) will cost $119.99. The Windows 8 Pro upgrade will cost $199.99.
Currently, Microsoft is charging $39.99 for an upgrade license to Windows 8 Pro from Windows XP, Windows Vista, or Windows 7.
Testers who've been working with Windows 8 preview builds also have been eligible for the $39.99 upgrade price. The Windows 8 preview builds (Developer Preview, Consumer Preview, and Release Preview) all expired earlier this week. After that time, users with those builds will notice that Windows 8 will restart every hour "until they've installed a released (RTM) version of Windows," a Microsoft spokesperson confirmed earlier this week.