I have a 11MB JSON graph file with about 45K edges and 73K nodes without x, y locations, and I want to display this graph using the BFS layout. I am using promise/defer
You are limited by the performance of the browsers themselves. Cytoscape.js uses several techniques to optimise rendering performance, but you'll still hit the ceiling of the browser's performance.
I don't think you'll find any browser tech today (July 2015) that supports rendering such large datasets.