(pure speculation) I think the iphone 4 won;t make it to ios 8 because the phone is reaching the end of its life cycle. Honestly I commend apple for letting the iphone 4 last so long! but its safe to the all iphone models after the 4 will get the upgrade! To iphone 4 users i would personally recommend to wait and see. If the 4 doesn't get the upgrade wait for the iphone 6. Then you will be ensured IOS updates probably until IOS 11