My boys were born at 30 weeks. Early, but not too early if you consider that fuul-term for triplets is 34-36 weeks. Nowadays, 85 - 90% of babies born after 28 weeks are free of complications strictly related to pre-mature birth. 

Bobby was 2 lbs. 14 oz. - had the most trouble breathing at birth, most trouble with feeding, septicemia at 10 days, small bleed, slightly enlarged ventricles. Perfectly healthy today. 
Joseph weighing in at 2 lbs even, did best of the 3 at birth - least problems breathing, started feeds first, etc. Sustained most brain damage in utero - ultimately died of complications at 20 months. 
Anthony was my biggest baby at 3 lbs. 2 oz. Had trouble with apnea but otherwise stabilized fairly quickly. Massive brain bleed from prematurity resulting in extensive PVL and ultimately diagnosed with spastic quad CP. He should be much worse off than he is though. Typical 4 year-old, no seizures, no concurrent medical issues whatsoever now (outgrew reflux by 9 months). 

We have friends whose twins were born at 24 weeks - one twin was 3+ lbs., the other a little over 1 lb. The larger twin died of pre-maturity complications at about a month of age; the smaller twin turned 5 last weekend. We went to her birthday party - Bobby has a hard time keeping up with her. :-)
Other friends we know: first child - full term, typical pregnancy, good birth weight, no apparent reason for the child's CP (she's in Anthony's class). Their second and third children were both more than 6 weeks early - perfectly healthy and typical!
Our babysitter, 17 years old (honours student, plays volleyball and rugby) was born at 24 weeks and weighed only 2 lbs.

You just can't tell. I'm sure if we polled the list, there are no common "causes" for CP. Even pre-maturity and very low birth weight doesn't necessarily mean anything. I agree that there will be more babies "saved" in the future but I don't know if the incidence of complications or the severity of those complications will necessarily go up. 

Just my thoughts. :-)

Yvonne
Mommy to triplets:
Bobby (nda);  Anthony (moderate spastic quad CP); 
and our Angel Joey {Apr.14/97 - Dec.31/98} (severe CP with many medical complications...) 
Ottawa, CANADA