"HCL promises upgrades are now easy"
They've been easy for a long time, development-wise. Heck, all the @functions from R3 (and probably from R1) are still there.
Notes/Domino has a long-established history of backwards compatibility, as far as developers are concerned. If you go to OpenNTF, you'll find plenty of apps written before R9 that still work. Maysoft has the Notes Document Viewer since forever (well, their copyright states 2002), and it is an extremely handy tool that I use regularly on R9 and R10 platforms. I'm sure it'll work fine on R12.
From a developer's perspective, I don't see what the problem is.
Of course, admins might have a different perspective, but I don't see that updating from R9 to R10 made any great difficulties in the companies I work with.
This announcement is just to remind Domino users that R9 is end-of-support. Well, okay then, but it won't prevent people from running their servers, no more than Windows XP has stopped running (and running, and running).
That said, R12 seems quite interesting, but obviously jumping from R9 to R12 is going to be a bit of a hassle.