I think the traditional PBX will have significant market share for the next 10 years because many companies will hold on to the old equipment. In fact, during the Y2K scare, many old-time computer programmers were enticed to come out of retirement because many government departments and businesses were still using PDP-11.
It doesn't really make a lot of sense for a company to get rid of its reliable traditional PBX and take a chance with Asterisk. On the other hand, a brand new company can save a lot of money by going straight to the Asterisk route. That's where Asterisk will be making significant gains in the market.
But if I started a new company, I would go straigh