After the planet's interior cooled for some 400 million years, tectonic plates began shifting and sinking. This process was stop-and-go for about 2 billion years. ... In another 5 billion years or so, as the planet chills, plate tectonics will grind to a halt.

How long will plate tectonics last?

As part of the ongoing supercontinent cycle, plate tectonics will probably result in a supercontinent in 250–350 million years. Some time in the next 1.5–4.5 billion years, the axial tilt of the Earth may begin to undergo chaotic variations, with changes in the axial tilt of up to 90°.

What will happen if the tectonic plates continue to move?

Volcanism would just continue on the big island. There would also be far fewer earthquakes, since most are due to motion of the plates. Erosion would continue to wear the mountains down, but with no tectonic activity to refresh them, over a few million years they would erode down to low rolling hills.