Blockbusters will still happen, franchises will still bloom, but their impact craters fill in much more rapidly with new materia.
I think your looking at the question through the prism of being a sci-fi fan rather than what is universally popular. Wars is definately one of the most popular franchises of all time - but Potter not only hit box office records but is one of the best selling works of fiction ever.
I think SW is without a doubt in terms of sci-fi one of the biggest impacts to the genre. However, Potter accross all age groups and that its been successful both on screen and in books eclipses Wars in terms of its cultural impact.