Lucas seems to have had a text crawl in mind from the beginning. From Star Wars: The Annotated Screenplays (note that the title crawl is referred to as a "roll-up"):
Like the story itself, the roll-up went through many different permutations. Initially, the first shot of the film showed a vast sea of stars, a planet, and five moons surrounding it. In the third draft, George Lucas simply used the sea of stars as the backdrop to the main titles and the roll-up. Originally, in the rough draft, the roll-up only defined the notion of a new Empire with its ferocious "Knights of Sith" (who became "Legions of Lettow" in the first draft) hunting down the legendary "Jedi Bendu" warriors (called "Dai Nogas" in the first draft). Eventually, the notion of civil wars, the Rebellion, and the Death Star were added to the text, providing the audience with more background information on the plot and the characters.
George Lucas: "The roll-up came out of the serial concept, which was that this was a series of movies and not a single movie. At the beginning, it was pretty long and unwieldy, and I kept paring it down and paring it down. [...]"
(Source: Star Wars: The Annotated Screenplays (1997), page 6)
This is corroborated by purported rough drafts of the original film:
A sea of stars is broken by the vast blue surface of the planet, Utapau. Five small moons slowly drift into view from the far side of the planet. The main titles are followed by a roll-up:
Until the recent GREAT REBELLION, the JEDI
BENDU were the most feared warriors in the
universe. For one hundred thousand years,
generations of JEDI perfected their art as
the personal bodyguards of the emperor.
The same title crawl appears on the first page of the Dark Horse adaptation of the rough draft for The Star Wars: