Last I checked, the Standard Model was still having slight problems with the strong force (and not-so-slight ones with gravity), with several competing theories, and QCD (Quantum Chromodynamics, which simply describes the strong force and does not itself try to unify it with any of the others) and electroweak theory (and quantum mechanics and general relativity) are the extent of what is known "for certain" (or at least has been confirmed experimentally thus far). It would appear that electroweak-strong unification is going to be next, but the theories still have a few wrinkles to iron out. More importantly, the all-important experimental work mostly isn't there yet, and what little there is (proton decay experiments, mostly) have yet to produce any conclusive results. What I meant to say is that the only way to know how things will turn out is to wait and see and pray that it happens in your lifetime.
String theory, which actually encompasses several different (and in most cases mutually exclusive) theories, does appear to be a good candidate for unifying electroweak and strong forces with gravity, if it can be made to work, but it's way ahead of experiment right now, and once you get too far from experimentation you cross the line between physics and "philosophy with lots of equations".
Wes, I think you misunderstood what I meant by the surface of the bubble being causally isolated from the interior. The issue I was bringing up is not that the ship wouldn't be able to interact with the universe outside the bubble (although this is also true and could also be a problem), but that the ship cannot interact with the bubble itself when the bubble is travelling at FTL speeds. Flashing the bubble is unnecessary (though it might make things easier on your gunners, and might be necessary for your missiles, fighters, and torpedoes to get very far in one piece) for combat, or other interactions with the rest of the universe, at sublight speeds, and wouldn't do anything to help make it possible to get the bubble from STL to FTL, steer while going FTL, or take the bubble from FTL back to STL if it were already going FTL. Only something in the surface (the regions where space is contracting/expanding), rather than the interior (the flat region behind the contracting region and ahead of the expanding region) where the ship usually is, could make the bubble transition between STL and FTL speeds (or between different FTL speeds) or change its direction of motion while at FTL speeds, and anything in the surface of the bubble would be destroyed, except a fully-formed black hole (and, as measured from outside the event horizon, it would take an infinite amount of time for a black hole to become a true singularity), so in practice your CDD would allow you to travel at relativistic speeds without experiencing relativistic effects (time dilation, length contractiion, mass increase).
All things considered, wormholes are the best way to go, since not only can they exist, but they can even be created and traversed (you'd need exotic matter to hold them open long enough to be useful, but you'd need it for an Alcubierre-type drive, and producing enough of it for either shouldn't be an insurmountable problem with the tech commonly avaailable in this setting). TTDs and other devices that take you from point A to point B probably have less to do with general relativity than quantum mechanics. FTL travel methods that rely on another universe or dimension in which distances are shorter than in ours (such as SW-style hyperspace drives, or "The Warp" used by Ayenee ships in the 2nd Draconian War) should work fine, assuming that said universe or dimension exists. Fold drives also may be plausible, though "folding space" as it is rather vaguely described, sounds like a wormhole by another name.