Was Martin Luther a Closet Universalist?

Here's a recent question sent over to me:

I recently heard a claim that Luther was a universalist, or at the least a hopeful inclusivist. Have you written anything on the blog about this that I missed? Based on this quote here "It would be quite a different question whether God can impart faith to some in the hour of death or after death so that these people could be saved through faith. Who would doubt God’s ability to do that?"

I don't recall this, so like everyone, I put the quote in Google.  The first thing I discovered was that back in 2011 I missed the brouhaha of the quote being used in Rob Bell's book, Love Wins:

Rob Bell on Martin Luther and Salvation in Hell (Justin Taylor)

Easy Virtues and Cruel Mistresses: Basic Advice on How to Interpret Luther (Carl Trueman)

Then, I even came across a Universalist website saying that Luther was being mis-cited: Was Martin Luther a Closet Universalist?

So, this is a quote in which I don't need to reinvent the wheel. Interesting stuff.