It seems like what all of this boils down to is that while Lucas was producing his movie The Star Wars, it was called numerous subtitles, the most prominant being 'Saga 1'. The only evidence of the subtitle 'Episode IV: A New Hope' appeared after the production began of The Empire Strikes Back, which was being produced under the company LFL named 'Chapter II' productions.

If George had the idea of calling the first installment of his movies 'Episode IV: A New Hope' before 1979, it could be possible; however the evidence of the other names strongly suggest that George was still making up his mind on where the franchise should start and even how many chapters would be included. No doubt the success of the film helped in the decision. Maybe 'A New Hope' was an earlier idea, but it no doubt was his only one for the title.