Could the Continents Shift Back Together?

Yes it is possible. The plates of the earths plate tectonic system are in relative motion that ultimately depends on circulation of platic rock in the deep earth. There is no reason why the crust that forms the continents could not again come together.

Will the continents merge again?

Just as our continents were once all connected in the supercontinent known as Pangea (which separated roughly 200 million years ago), scientists predict that in approximately 200-250 million years from now, the continents will once again come together.

Can Pangea happen again?

The last supercontinent, Pangea, formed around 310 million years ago, and started breaking up around 180 million years ago. It has been suggested that the next supercontinent will form in 200-250 million years, so we are currently about halfway through the scattered phase of the current supercontinent cycle.