In the yahoo article, the Toronto Marathon race director made it pretty clear that without timing mats, photographic evidence is what they'll look at if there is a question about the results. He says that without photographic evidence the burden of proof is on the runner to prove he completed the course.
If that is the standard, there is overwhelming evidence for a DQ.
It's going to take some time, there are 19,000 photos to go through. I know they've already been gone through by industrious people on this board, but whoever runs the investigation can't just take the internet's word for it, he needs to verify. That will take a time.
They are probably also hoping that if they give it enough time, someone will step forward with some kind of smoking gun evidence. They don't need anymore evidence, but they'll avoid any bad PR that might come from DQing him based on only circumstansial evidence.
I'm guessing May 22 is when his name is stricken from the record books in Lehigh, Boston follows suit shortly thereafter.