FWIW, they just destroyed the earnings record, so things must be going good. I'd wager that a nMP has something to do with that record..as well as the iPhone 6. Don't really see where adding this or that to the nMP is a true need at the moment. They seem to be riding high.
The Macintosh shipment numbers are public knowledge (it's released as part of the shareholders report), and the record earnings were pretty much entirely due to the iPhone. Mac was up, but not more than it's been up quarter over quarter in previous quarters.
Using your logic, they shouldn't upgrade anything, the iPhone and iPad included. But they will, because if they upgrade they can push even more volume. It's not like Apple just says "Whelp, we broke some records. Send everyone home! We're done! Cancel the iWatch! Everyone must be happy, so why bother?"
(There's also plenty of people in this thread saying they're waiting to buy until upgrades are made, which should be a hint to you that, indeed, there are sales Apple is not getting right now.)