First of all, Will isn't Jack. And even if it was, there are some successful Jack stations like the one in LA that are sustaining and even growing from their initial success.
The guy consulting NextMedia on Will is the same guy behind most of the Adult Hits stations that are going by the "Bob" name. Bob stations in Norfolk, Austin and Pittsburgh are doing incredibly well--especially on a 25-54 basis--and are showing no signs of shooting to the top and then fizzling.
Will Will win? That depends on how well it is executed and whether NextMedia provides the appropriate level of marketing support. But to write it off with comments like "The Jack Formats are dying" demonstrates a pretty high level of cluelessness.