What evidence (real data, not made up) do you have that supply is outpacing demand? Keep in mind, investors are NOT the supply. LEGO factories are the supply. A LEGO set in the hands of an investor isn't 2 LEGO sets, it's still just one. LEGO, as we all know, attempts to limit the affects investors have on the overall supply in the short term. Investors who buy and hold create an artificially tight supply in the short term, not the other way around. Resellers cannot affect the supply, only the current price point. In the end, only LEGO controls the actual supply. And they are pretty particular about not oversaturating the market.
For the record, Brickset shows (359) 2014 releases, which includes all promo items, poly bags, juniors, Duplo, collectible minifigures, etc. Just so we're using real data. I would say 2014 is probably an anomaly with the Movie sets being an extra theme, 2 collectible minifig releases, etc. Time will tell. I am not worried.
For the record, Amazon sales have been steady for me in 2014. Same with BrickLink. I don't do much on eBay.