The NSA could probably STILL access the information if they want to
Sure, they could resort to rubber-hose cryptanalysis, targeting key Google employees. If it were to come out, though, it would make the Snowden leaks look very, very mild. As one of said key Google employees (I work on security infrastructure), I've been given to understand that if I am ever approached in any way by the government, I am to immediately consult with Google legal counsel, and that any request that I not talk to counsel would be illegal (I think it would violate the constitutional guarantee of due process).
or Google can be compelled to reveal it with a super secret demand order, or even a regular warrant.
Certainly, as long as the order or warrant is issued by the appropriate court, is not excessively broad, etc., and then Google will add it to the statistics for the transparency report.
No information that is ever collected is ever "safe" from prying eyes.
In an information-theoretic sense that is undoubtedly true. In that sense, though, I'd argue that nothing that touches a networked computer is safe.
And even Google having the information is certainly nothing to be comfortable about.
YMMV, of course, but I actually am pretty comfortable with it. Of course, I have visibility into how Google manages user data, which helps. There is the possibility that a future version of Google may behave differently, but I think that possibility is at least a decade or two away, because I think it would take that long for the company's culture to change enough to make it possible.
They have ENOUGH information about consumers already... certainly enough to be creepy.
Perhaps. I think the general belief about what data Google has overstates the reality by a wide margin, and further even where it's accurate it overstates Google's (current) ability to actually make use of the data.
In any case, if you're concerned with it, Google provides you with the tools to opt out. I encourage you to use them. Personally, I turned on web history, location history, route all of my email through gmail, use Hangouts for SMS, etc., etc. I find the value I get from the services to outweigh the risk I perceive. If you see that balance differently, you should act accordingly.