Things do move fast! But I sometimes wonder if perhaps we are approaching some natural limits to technology. Sure, there will be progress, but maybe not as fast as we've gotten used to for the last couple of centuries. We may not be able to build everything we can think of, and just because the laws of physics may be consistent with a proposed invention doesn't necessarily mean it's just around the corner, or even possible.

I highly recommend "The Starflight Handbook: A Pioneer's Guide to Interstellar Travel" by Eugene F Mallove and Gregory L Matloff (John Wiley & Sons, 1989), as an authoritative introduction to potential advanced propulsion systems, written at a popular level, but with enough algebra to make it legit. Hopefully, a more up-to-date edition is now in print. It is a great introduction to possible space propulsion systems now being discussed, and it evaluates them critically. A number of Bussard Ramjet variations are discussed and their strong and weak points assessed. Most of the other systems are also examined, from nuclear pulse, various fusion reactions, variations on the rocket principle with fusion/fission options, solar sails, beamed energy, ion scoops, and THEN some "novel advanced propulsion concepts".

I got the impression that interstellar travel is not going to be impossible, but it ain't going to be very easy, either. None of the options presented is without serious difficulties, but I'm optimistic enough to think that there must be at least one, or some combination of several, that may some day be viable.