Dinosaurs never truly went extinct cause they are in our world today in form of birds. Dinosaurs are the direct ancestors of birds just in the same way our grandparents and great grandparents are our direct ancestors.
But the true question is can a dinosaur like the Tyrannosaurus Rex (T-Rex) ever be seen again? But as you could probably tell the answer to that question is a straight up no.
Unlike you and your grandparents where there is only one generational difference which are your immediate parents, there are billions of generations between the birds in our world today and their ancestors which are the dinosaurs. Due to this very long line of evolutionary trend between the dinosaurs and the birds we see today, is why they act and sound completely different compared to their ancestors.
To fully grasp this, the knowledge of evolution has to be well understood, evolution is the process that explains how living things evolved from past living things billions of years ago. Several living things evolve in their own way to ensure maximum survivor. After the cretaceous-Paleogene (k-Pg) extinction event that occurred 66 billion years ago, which wiped out about three-quarters of all plants and animals species on Earth, birds survived this extinction event, and thanks to their already small appearance they were able to feed on insects and little seeds and also due to the presence of wings was able to scout far distances in search of food and shelter. Though provided another event such as the previous one that wiped out the dinosaurs 66 billion years ago were to repeat itself, no animal in the world today would evolve back into a dinosaur because the aim of evolution is to lead to a more progressive generation rather than going backwards to what it used to be.
For any animal to be a dinosaur of any kind, it has to come from a group known to scientists as ‘Dinosauria’. These means that the Triceratops and modern birds has a common ancestors, with birds being the last surviving specie of the group Dinosauria. This ultimately means that if dinosaurs are ever going to exist again they can only Come from birds.
https://youtu.be/XAzGC89n0S4 (This animated video can help you better understand how dinosaurs evolved to birds).
Several animals belonging to the group Dinosauria has gone extinct, including the sauropods, stegosaurs, ornithopods, ankylosaurs, ceratopsians and non-bird theropods. The birds in the world today are from the theropods. However, birds of today have very different genes compared to their ancestors because the more generation pass between ancestors and descendants the more the gene modification and differentiation.
Again, for a bird to even start to transform or evolve into a dinosaur, a lot of changes and modifications would have to occur in its body, such changes include transformation of wings to fore limbs and additional of two more fingers on its feet to make it five as seen on the Triceratops, also the would need to grow scales all over their body and not just at their feet as seen in the Tyrannosaurus and Triceratops and to be able to even do this they would have to lose all feathers which are get vital to them as it aids them in flying and also staying warm.
All these considered it is highly improbable that birds will ever evolve to dinosaurs again.