It's the velocity of the wormhole itself, not the velocity of the transition, that gives rise to time travel.If you had these portals, but they had a delay system so that they operated to only allow passage at or below 'c', it would not fall prey to the issue of time travel, right? In short, if you teleported (scifi) halfway around the Earth, but you stayed just below 'c', you would just have a REALLY fast trip, without Relativistic complications, right?
Imagine you are hanging in space in a ship with a wormhole. At rest relative to you is another ship with the corresponding wormhole. When one of you starts speeding up the wormholes fall out of sync so to speak