New 6th Edition rumours have the Deep Strike rules re-worked as "strike down, then shoot immediately".
http://warhammerswede.blogspot.com/2011/10/callidus.html
EDIT: Rumoured changes coming in 6th edition is Deep Striking units being allowed to shoot immediately upon entry into play. Maybe I'm grasping at straws here, but there's a few possibilities:
A. The rumour is full of crap.
B. Rumour true, but Polymorphine rule changes to make the Callidus essentially stay the same.
C. Rumour true, Polymorphine changes differently or is clarified or Callidus is otherwisely changed (my guess).
D. Rumour true, Polymorphine wording is unchanged, all of a sudden Callidus is looking a tiny bit better. Not good, but better.