If i were to guess before the next gen console specs were announced what the RAM would most likely be I would have said 4GB.
I think 8GB was the right move and give's companies more room to ex[and in the next generation.
The biggest problem I saw with the last generation was some companies (Bethesda) going about 5% further than the console could handle.
This is the Game of Thrones
Where you either win
or you DIE