This is NOT Speculations. I must NOT speculate. I must NOT guess. No SWEGs allowed here.

 

How might we estimate how far a planet has migrated?

 

How might we estimate how far it might yet migrate?

 

We have any number of "Hot Jupiters" in very close orbits around other stars. They are not believed to have formed there, but way out -- several AU out. Are we to estimate they migrated five to ten AU to their present locations?

 

Our own familiar Jupiter is said to have migrated. Is there a way to tell?

 

When you all first told me this, I quit guessing and speculating that the no-doubt mythical "Niburu" had done certain damages in the inner SolarSystem. I started guessing and speculating that Jupiter (Or another, since-vanished giant) had. Now I shall have to wait another hundred years for clues about that.

We haven't got an exact science on planetary migration. Each system will vary depending on factors such as density and size of the protoplanetary disk, mass of star, composition of the disk, other planetary influence etc.

 

So answering your last set of questions requires considerable research on the factors I mentioned as well as other possible influences