By the time I will be able to drive will the older versions of the Scion xb be to old to drive?

they wont be too old to drive...kids are still wanting the 1991 honda crx and thats a old car...i want a 1972 datsun 240z and now thats an old car....but yes the engine can be swaped out...most people swap it for either the 1zzge or the 2zzge engine...which you find in the corrolas and the celicas...