If AI x-risk is 50%+ now, it was 50%+ then, people just didn’t realise it very well. Unless you think EAs focusing on AI x-risk was the sole factor that pushed x-risk from 5% in the next century to 50%+ over whatever timelines you now have.
If you meant the perception of AI x-risk from EAs, as opposed to the actual risk level, I think the closest to an “EA number” we might get is 10% from Toby Ord’s The Precipice—this was considered the most likely x-risk in the book (with the total being estimated as 1⁄6) and was enough to get me to start looking into the problem in more detail.
I don’t think this is something anyone on Earth knows with mathematical precision, I’m afraid.