As you say, we have 1G and 10G in use today, so we'll soon need more. But 100G is ALREADY a standard. I'm sure we'll need and get 1T eventually, but 100G should be enough for almost everyone for a few years.
BTW speeds of many Tbit/sec were demonstrated in the lab a good 10 years ago using optical dense wavelength multiplexing, but full product development was too expensive for what the market needed then. Also, it was aimed at large telcos, not as the cheap plug in connection that Ethernet implies, But technology moves on, it will happen.