Well, both of these methods are being used, and by the time that you people are as old as I am, we should know for all the nearest stars whether they have planets going around them or not. We might know dozens or even hundreds of other planetary systems and see if they are like our own, or very different, or no other planets going around other stars at all. That will happen in your lifetime, and it will be the first time in the history of the world that anybody found out really if there are planets around other stars.
His stress on "even hundreds" shows that even he thought this figure was unlikely. Sagan was 47 at that time, so assuming the kids were about 12, he was hypothesizing into 35 years to the future, to 2015. He would have been pleasantly surprised at the progress so far, I think.
I wonder if any one of those kids have looked at this page and thought of that day.
At the onset of the great exoplanet discovery breakthrough in the mid '90s only a few very meagerly funded teams working were actually searching. Once they started to find planets then the astronomical community started paying attention, and funding as well as access to the best observatories in the world started pouring in.
Also, an interesting point of fact is that Sagan was actually hugely excessively optimistic. The two techniques for exoplanet discovery he describes are direct observation through occultation or deep nulling of stellar light and astrometry. As it turns out, these techniques are very, very difficult to use and we have not actually built any special-purpose spacecraft that use either method. To date only one planet has been detected through astrometry, for example. But there are methods which work rather well (doppler radial velocity and transit detection) though they were not familiar to Sagan.
EDIT: Here is an amazing video showing all known exoplanets orbiting one star, so you can see their relative sizes, distances, etc.:
Nearly every single exoplanet discovered is within the orbit of Mercury.
Edit: Here's the graph just up to 2012: http://exoplanet.eu/diagrams/?t=h&f=&x=discovered...
The future of our species is huddling around the warmth of the campfire (sun) and using raw materials from the asteroid belt to create structures orbiting the sun, until we create a sphere around the sun and all space is exhausted... then.. maybe after another few hundreds after that point, will these planets become useful. But not for reasons we would think. Perhaps for research purposes to see if humans then have the capability to tune back in to evolution after a thousand years of being pampered and letting the DNA deteriorate by eliminating survival of the fittest.