There are a lot, and it is possible that new ones can make inroads.
But there are a number of good open source or free vulnerability scanners. Skipfish from lcamtuf is extremely fast. Burp from Portswigger, which seems to do very well in head-to-head comparisons has a free version. It is very actively developed and has a very large feature set.
Here is a comparison chart of scanners: http://www.sectoolmarket.com/price-and-feature-comparison-of...
A lot of thought would have to go into what features does the market feel are missing, and how difficult is it go get the coverage needed.