Well the problem there is that it's a theoretical upper bound, which is another way of saying "we have not yet found a specific reason that 3.5 inch 60TB drives should be impossible with this technology". That is a far cry from "on their way".
So now, a top of the line Xeon is faster, has 10 multi-threaded cores, includes AES acceleration, and uses 20% less power than it's predecessor 3 years ago... thanks to that base technology.
If you're running a business that generates/consumes alot of storage, this announcement means that you need to start thinking about how to deal with a petabyte of storage capacity with performance characteristics similar to what you have today. (for 1/30th capacity)
Today you can fit about 96T into 4U if you squeeze a little. That's 48 spindles then, sharing the load.
With 60T drives that turns into 2.8P on the same 48 spindles.
At today's maximum SAS bus-speeds (roughly 10 GBit/s) it would take 33 days just to write such an array full (assuming all components can sustain that throughput).
And let's not get started on IOPS...
Anyway, it will be a while before 60T drives hit the shelves. Until then at least the bus-speed issues will probably be sorted out.
I'd say it's a big deal that Seagate claims they will develop 60TB HDs with your usual exponential growth curve (bearing in mind we're starting at 2-6TB.) "On the way" doesn't mean tomorrow.
Seagate's press release makes it sound like there're no other HDD manufacturers in the world besides them.
Another way to look at it is to see how many bare drives are being sold at those specs (1TB 2.5") vs. external drives. The bare drives won't sell as well if they are a non-standard height (at least I assume they wouldn't).
Many laptops will also accept the thick 12mm drives you're referring to.
Main content is: The maximum capacity of today’s 3.5-inch hard drives is 3 terabytes (TB), at about 620 gigabits per square inch, while 2.5-inch drives top out at 750 gigabytes (GB), or roughly 500 gigabits per square inch. The first generation of HAMR drives, at just over 1 terabit per square inch, will likely more than double these capacities – to 6TB for 3.5-inch drives and 2TB for 2.5-inch models. The technology offers a scale of capacity growth never before possible, with a theoretical areal density limit ranging from 5 to 10 terabits per square inch – 30TB to 60TB for 3.5-inch drives and 10TB to 20TB for 2.5-inch drives.