Gig economy is taking over industries and consulting is no exception. Global management consulting industry is said to be worth around USD 260 - 300+ billion, depending on how much we blur the line between management and technology consulting. Another research says that 20% of the industry works in micro-consulting firms (freelancers included). If we ponder it by the difference in average contract size, we get approximately USD 20-50 billion.

Of course, the trend can be easily observed in a rapid growth of freelancing consulting sites (e.g. as this one).

My personal opinion is that it's not really an opinion, but rather a fact. However, the question can be observed and discussed from multiple angles. If you want to get more info, feel free to contact me. :)