The evidence for Planet Nine's existence has continued to grow over the past nine months, as several different research teams have determined that the orbits of other small, distant objects appear to have been sculpted as well. Astronomers have said Planet Nine is perhaps four times wider than Earth, and such an object would be easily visible with professional-grade equipment if it were relatively close to Earth.
With all the new technology at their disposal scientists will finally be able to prove the existence of this big planet. Evey day we are developing new ways to see what's out in space. In the years to come we may find even more planets that we never knew existed before.
Scientists have both the technology and the resources to explore space further than it has been explored before. I think they'll discover this planet if it is there. It's going to be a cold planet, that's for sure and I hope that scientists one day discover another sun with a planet at just the right distance from it. Till then, they should keep on looking for planets closer to our solar system.
There is no way that something that size has existed in our solar system for all these years without someone discovering it. Anyone can use a decent telescope in order to see the planets that we know exist. With as much space exploration as we've had, there is no way that something that large would have gone undiscovered.