Perhaps the world's foremost fashion critic, Suzy Menkes, who doesn't usually partake in rumor-mongering, started a raging wildfire with the first line of her Milan report in today's New York Times: "If Raf Simons ultimately takes over the helm at Yves Saint Laurent — as those familiar with the situation in Paris suggest — the designer will have found a sweet spot for his meticulous modernism." The interwebfacetwittosphere then went into a tizzy when her associate Jessica Michault tweeted: "Suzy Menkes breaks the news that Raf Simons is slated to take over the helm at Yves Saint Laurent. Read it online on the NYT."
For several seasons now, YSL's current creative director, Stefano Pilati, has been dogged by reports of poor sales and rumors of replacements. Suzy Menkes' bombshell is the latest in a long line of speculation, but surely the most credible to date.
Of course, it's worth repeating that at this stage it's just a rumor. Nothing is confirmed until an announcement is made. That said, Raf Simons at YSL is a very, very intriguing idea.
Update 9/26/11: This morning YSL responded to the above with the following statement: "Yves Saint Laurent disclaims and regards as unfounded the current rumors concerning the creative direction of the house. Stefano Pilati continues to dedicate his talent and energies to Yves Saint Laurent and the coming fashion show."