it would be a very unprofitable move to shut down Knack; and, if Google or some such entity ever purchased it, yes it is a possibility but I didn't lose sleep over it until you mentioned it today. Only Yahoo would be shortsighted enough to sunset something with the potential of Knack.
Knack and its predecessors (Knack's done a much better job of making this easy) have essentially commoditized programming into an unspecialized task. Someone who understands logic can now "program" and piece together everything they need, especially with tools like Zapier.
I can only imagine that Knack will improve, incorporate more features, and add tens of thousands more users-- and do this all at an increasingly faster rate.
I cannot imagine any entity would shutter the growth or take the team in-house, given the huge potential that knack has to capture #1 market share for this new emerging market.
And if they shut down, I will just google "easy database software" and go with runner-up, kinda like I did the first time around.