VoIP Magazine has an article about VoIP Growth. Excerpt:

The sales of VoIP equipment to carriers will increase from 2004's $1.6 billion to $4.7 billion by 2010, according to a recent report by Dell'Oro Group.

While class 4 switches drove the market when next-generation equipment was first introduced, sales of class 5 switches are now playing a significant role in the market's growth.

Both class 4 and class 5 products are expected to have an increase in sales over the next few years as the interest in upgrading the circuit-switched PSTN to the IP-based NGN continues to increase.

As the article touches on, IMS is certainly going to be a huge driver in this growth. Many service providers are looking to upgrade equipment immediately to take advantage of IMS and the benefits that come with it.