Those predictions speak by themselves:

Frost & Sullivan (2000):

"Internet telephony, also know as Voice over Internet Protocol, is expected to have hit $266 million in revenues worldwide in 2000, up more than fourfold from 1999. Sales are forecast to explode to $349 billion in 2006."

"The long-distance wholesale voice services market is set to catapult from $19.85 billion in 1999 to $57 billion by 2005."

Frost & Sullivan, World VoIP Services Market (2001):

Wholesale and retail VoIP
Estimates the number of voice-over-IP minutes used worldwide by businesses will balloon from about 497 million minutes this year to 127.5 billion minutes by 2005.

Ovum expects next-generation services revenue to grow from $74 million in 2000 to nearly $40 billion in 2006.

The Phillips Group-InfoTech (2000):

50% of retail traffic will be IP by 2003. This will lead to a tripling of the wholesale service revenue to $116 billion in 2003, with IP wholesaling adding $16 billion to our original forecast of $100 billion for current wholesale services.