The maximum capacity of today's 3.5 inch hard drives is 4tb, and has been since last year. I know it's a press release, but that's bending the truth a little too far for my taste.
The meaning of the title is that Seagate is claiming that after a few years of stuttering they've jump-started exponential growth for the HD once again.
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.
And I've got a 2.5" 9mm internal one, but I'm fairly sure that they're talking about density per platter and all 2.5" HDDs larger than 750 GB seem to use two platters.