@hrishi I agree that they need to start pushing other colors (and giving them blue mechanics). We'll never see ancestral or walk in another color, but we could see a cruise/dig in another color. They'd be in flavor too. Maybe something like "Bargain in Blood - Instant - BB: Pay X life to look at the top X cards of your library. Put two of them into your hand and the rest on the bottom of your library."
But even with that, I think the threshold is FoW. Back in OS days, blue had walk, twister, and ancestral - and other colors could compete. Once FoW came out and the format sped up, blue was the ONLY color with an out to turn 1 wins. And to run FoW, you needed a critical mass of blue cards to support it, so that pushed other colors out even further. If there was a card like "Force of Death - 2BB - Instant - Counter target spell and lose 2 life. You may exile a black card from your hand instead of paying the casting cost," you'd see mono-black or black+ decks being played.