There certainly could be some of that, but given the lower cost of SSDs, we see Apple still using mechanical drives in their iMacs, and I think industry standard SSDs, instead of the blade models would also be better.
I'm not sure what "industry standard SSDs" means - if you're talking about a SATA drive... that's the 5400 RPM version of Flash. You'd rather have that than a PCIe blade day in and day out, on the chance that some day you'll want to replace or upgrade it? The only reason SATA SSDs are the dominant SSD form factor is that they fit into desktop PCs that are (still) built to hold mechanical HDDs. Are all those ultra-slim PC laptops equipped with SATA drives??? The day the industry abandons HDD-equipped desktops they'll abandon the space and hardware required to secure and connect a SATA HDD - everything will have a blade or soldered Flash, just like RAM.
And to play with words a bit, in desktops, SSDs are not yet the "industry standard." I sure don't see all-SSD base configurations at Dell and HP - they're optional. Even Dell's $5,816 (list price) Precision Tower 7000 workstation comes with a SATA HDD.
The cost of SSDs is lower than it was, but still nowhere near the cost of mechanical drives. If Apple is going to retain price point on those models that have mechanical drives, it means a line of machines with substantially smaller internal storage and a lot of users hanging an external HDD off the back - a problem faced by countless owners of 128GB MBAs.
Of course, those external HDDs might go away if Apple still sold towers/pizza boxes with spare drive bays. Right? But the vast majority of computer users would not open an "easy-to-upgrade" tower and slap another drive into a spare slot, any more than they'd change the oil in their car. They'd still buy an external drive, because plugging an external into a USB port is cheaper and easier than having a shop install an internal.
Product design is a careful balancing act - purchase price, performance, reliability... I fully appreciate that a portion of the market would prefer a higher emphasis on repairability/upgradability. But far greater numbers do not - they want to drive their cars, run their household appliances, and enjoy their home entertainment products with a minimum of maintenance or fuss. The day of the PC as hobby is over. The vast majority of users are just that - users.