That's a remarkably frank apology from Valve. It's rare to see this level of frankness from a mainstream organisation. I'm actually rather impressed.
Having said all that (and as stated in one of the posts above), it's wise to remain vigilant. It's likely that this idea hasn't been shelved entirely, but simply placed upon the back burner until a more opportune time/game manifests.
As an aside, I'd like to imagine a scenario in which a Bioware executive released such an honest and frank explanation in relation to one of their various misdemeanors.
"Yes, we deliberately limited the action bar to only eight slots because creating an entire new interface for the PC would simply have been too much work, we needed to ship the game in a timely fashion, and therefore had other priorities that we considered more important - What you get is a pure console port with some minor modifications for PC compatibility. Sorry, but that's the way it is"
I'd have felt far better about the whole thing if such a frank admission had been released, rather than hiding it behind a wall of PR speak and making out that it was a feature.