Roster limits, whether it's 25 or 26, will always mean that starting pitchers that can go 6 or more innings will have greater value than others. They won't be doomed, just harder to find and more expensive to pay.
As I said in a previous thread. I think traditional starters are doomed. As Fangraphs notes the average innings per start has been getting lower and lower over the past several years.
The nature of the game I believe is based on pitch counts now. Sure it's great to have guys who can throw 100 pitches over 7 or 8 innings, but I think there aren't that many guys who can do that any more.
We're gonna move to 3 innings per pitcher and hopefully the effective guys won't get through the oppo lineup more than once.