You actually bring up a good point. All cutting edge research in science, no matter what field they are in, contains such suppositions. This is the type of research that tends to make the news. Usually, when a press release is made, there are some solid facts about the subject while some further verification is necessary for many of the finer points. If it was all solidly known, it wouldn't be very cutting edge, would it?
By the time something makes it to the level of a good textbook on the subject (which can take years or even decades), though, there has been much more peer review of the subject, and much more verification & testing. This is not to say textbooks never make mistakes (even the best ones occasionally do), but that by the time the process has worked to this level, one can be assured that the central tenets of what one is reading are correct (in a reputable text, anyway).
Science always attempts to improve itself through time; theories that are broad in scope are almost never completely discarded (they don't need to be) - they are refined and brought into better focus. The basic core tenets of evolution, gradual change through time, have not changed since the time of Darwin. What we see now, though is positive identification and evidence that refine the detail of his theory in ways Darwin could never have dreamed.
It also is an (un?)fortunate fact, though, that science has become so complex that the finer details of the supporting evidence for theories take many, many hours of dedication and time to understand -- to those without the time and/or desire to do their homework on the subject, the results that science presents can indeed look like a potpourri of nonsense and proposition of faith, even though they aren't.
This is not to say textbooks never make mistakes (even the best ones occasionally do),
I know ONE textbook that has no mistakes in it.