As far as the TRex goes, we may well build a very lifelike TRex robot in 100 years that "walks", "breathes", "eats", "defecates" and "urinates" (given our infatuation with dinosaurs this is almost inevitable as our technology advances - a "real" Jurassic Park of a sort, if you will); however, it will still just be a robot made out of space age materials and requiring some mighty fancy computer programs to keep it stable on just two feet.
But resurrecting a living TRex will not happen because dinosaur DNA is long gone. Now, genetically re-engineering an Ostrich or an Emu to (re)-grow teeth, and also claws on its "wings" and (re)-grow a longer tail, by finding a way to switch back "on" recessive genes governing these features (IF they exist and IF we can identify them) is more theoretically possible (if we are correct that these are descendants of theropod dinosaurs as most evidence now appears to indicate); however even such a scenario is still solidly within the realm of science fiction.
Oddly enough, you may be incorrect on that point.
Not that there are any live T. rexes left, but I do believe if we needed some T. rex DNA, it would be readily available.