the potential to confuse less-than-technical users
>>On the downside, both the dialog and site also look like they have the potential to confuse less-than-technical users
Computers generally have this effect on less-than-technical-users. There is no way to warn such a person "you need to update your OS" without risking confusion, because they don't know what terms like "operating system" or "Windows" mean.
My mother falls into this category so I'll wait with interest to see if she asks me about it.
But - won't this functionality rely on you having auto-update turned on in the first place?