With 4 it's more of a CPU/GPU issue than it is RAM. With 4S it's quite a bit better overall, given a much better (dual core) CPU/GPU. RAM certainly plays a role too, but not the main one really.
Exactly this. The 4.7 iPhone 6 only having 1GB of RAM compared to the 5.5 would be stupid, it would bottleneck so many more iPhones... Also, they tend to increase RAM on each "big" iPhone release. iPhone 4 got 512MB of RAM, iPhone 5 got 1GB, etc... I think this pattern would make the most sense to continue, even if they are releasing 2 iPhone 6 models. Would save them having to increase the RAM in the 6S update. Just looking at how there already are bottlenecks on the newest line of devices, all RAM related, I don't see any iPhone 6 getting 1GB of RAM...
Don't even get me started on how bad of an idea 1GB of RAM is on the current iPads either lol.
The iPhone 6 4.7 would be more of an iPhone 5SS, just redesigned if it had 1GB of RAM.
Anyway, I have a retina mini now, and I don't see how iOS 8 could be all that bad. I have seen videos of iOS 8 on the iPad Air and it looks perfectly fine, hardly any difference in performance between 7.1.2.