Resizing terrain

I have a terrain that I sculpted and painted, I used 4 textures. The resolution is 500x500, lets say I wanted to resize this to 1000x1000, will my textures "stretch" or become degraded? They look the same to me, but I wanted to know how this works exactly. As long as the resolution size is even, does this affect the quality of the already painted textures?

 

bump (is this in the right place??)