While small it appears that the tournament funding for the SC2 scene has been diminishing slowly since 2012 before the expansion was even released while it is also being "out-popularized" by MOBA games in which the funding has increased exponentially.
Although an incomplete list this article shows that the quantity of quality titles coming out has diminished over recent years. Granted it takes more money and time to create AAA titles now so that must still be taken into consideration I suppose. As for the actual number of players playing these games it's entirely my speculation that they're decreasing. I don't see much hype or discussion about the genre (even though someone just recently started a hype thread about C&C on this board!)
I still believe over time investors will continue getting less confident with the genre opting instead to continue producing FPS titles and MOBA games in the already over saturated market.