Those designs probably aren't in Altium. They're probably in something like Mentor Xpedition or Cadence Allegro.

This is why I suggest that Altium is likely to be the first victim.

The non-Altium proprietary systems have a lot of legacy to hold them in place (like parts database integration across your company). In addition, they do have some very advanced features around routing matched memory buses and the like.

If, however, your design doesn't need that, KiCad will cover you, and Altium won't bring anything you need to the table.