This might be more of an IMHO subject, but I’m looking for whatever might have been developed, compiled or decided at some authoritative level rather than Doper 'pinions. (Sorry.)
How do you formally address couples, especially married couples, of the same gender? I’m interested in general answers but the specific question on my mind is this: if for slightly humorous purposes you wanted to refer to “Mr. and Mrs. Smith,” how would you translate that to a male couple?
I’m not an etiquette professional but my default assumption, unless I knew otherwise, would be that the two people in a same-sex marriage kept their original names. So I would go with “Mr Smith and Mr Jones” or “Mrs Smith and Mrs Jones” unless I knew that one or both of them had taken a new name after the wedding.
But what it’s alias Smith and Jones, hmmm? (Sorry, I actually liked that show as a kid.)
You’re right, I guess we have to differentiate between a couple that took a shared name and one that retained their own name. I’d guess that the latter is still far more common in SSM.
As for Mrs., isn’t that a tainted term among women ‘enlightened’ enough to consider SSM? Would it be Ms. and Ms.?
Is there any plural for Mr. other than the gaslight-and-spats ‘Messrs.’? And for Mrs./Ms.?
ETA: A further issue might be that with SSM we have formally dispensed with any lingering notion that one member is “senior to” or more important than the other…
The plural for Mrs (& Ms) is Mesdames (French just like the plural for Mr).
In the hotel where I used to work the bookings program had the option of “Mr. and Mr.” and “Mrs. and Mrs”. If someone booked under their name and there had for some reason been no way of asking but we did know they were a couple of two gents we would book it as “Mr. and Mr. Smith”. (With no other information available we would also say "Mr. & Mrs. Smith, what can you do?) If there was an opportunity to ask I would often politely enquire: “can I book that as Mr. and Mr. Smith?” Then they could either give the other Mr. a different name or stick with what I had. Obviously it was also often just “Mr. Smith”/2ppl.
To my knowledge nobody was ever offended or hurt or confused. We did sometimes get complimented by gay couples from other countries. That was nice 
Y’all.
So far, married couples of the same gender tend to keep their original last names, so they’d be addressed the same way a married heterosexual couple having two different names would be addressed.
I’ve seen that as “Sharon Lee and Steve Miller.” If titles are involved, it would be “Ms. Sharon Lee and Mr. Steve Miller.”
Thus, a same-ses couple would be “Mr. Terry Wilson and Mr. Harry Lannan.”
I suppose it’s less common these days, but I suspect hotels and motels once had a macro or a rubber stamp for “Mr. and Mrs. Smith.” 
My husband took my name, so we’re Mr. and Mr. X.
At the end of the day, or the beginning of the wedding invitation, you really just need to ask
FWIW, all the married same-sex couples I know hyphenated their last names.
As for the OP, I’m not really getting the point of the question. Are you asking how to distinguish between the two Mr. Smiths or Mrs. Smiths? I don’t know if the etiquette experts have addressed this issue yet, but the obvious solution would be to include their first names. While same-sex marriage is relatively new, having to distinguish between multiple adults of the same sex with the same last name isn’t a new problem. The Smith brothers would be addressed as Mr. John Smith and Mr. Robert Smith.
And you’ve managed to sneak that password past your sysadmin? Wow.
In real life, I use Ms. as my default. But if for some reason I wanted to emphasize that two women were a married couple I’d refer to them as Mrs. and Mrs.
I still wonder if Will Smith and Tommy Lee Jones got cast in Men in Black just because somebody thought it would look cool to have “Mr. Smith and Mr. Jones” on the poster.
No, actually some of us enlightened women have no problem with “Mrs”, be wary of assumptions.
Personally, I’d go for “Mr and Mr Smith” if they have the same name, or “Mr Smith and Mr. Jones” if they don’t. “Ms and Ms Smith” or “Ms Smith and Ms Jones” for women as a default (unless they wanted “Mrs”).
Think of a hetero married couple who are doctors. Wouldn’t you say “Dr. and Dr. Smith” or “Doctors Smith”, or “Dr. Smith and Dr. Jones”?
Are you sure you’re not remembering Alas Smith and Jones?
My daughter and her wife both kept their own last names.
What took me a while to get use to is that they both refer to the other as ‘wife’.
If both partners took the same last name or order of hyphenation, I think you’d have a situation where a brief abbreviation for plurals (Misters and Mistresses) would be useful. I guess there’s already Messrs, but we seem to lack a plural for Ms, Mrs, or Miss.
Hell, when in doubt, ask. They’re probably not going to be offended if you ask them how they prefer to be addressed as a couple.
I call them “Renee and Tracey,” usually. I presume that we will work something out if wedding invitations are involved.
Part of it was general curiosity about how society + the individuals and couples involved are resolving this new land in etiquette.
It stemmed from a need to use a male-male equivalent for the situation where you would humorously and over-formally refer to a couple as “Mr. and Mrs. Jones” - such as introducing your brother and his wife to a family gathering. I guess there isn’t one universal enough to make the joke work. Yet.
I’ve never run into such a situation where I had to figure out what to write, since I don’t use honorifics, but I’ve seen Mr. and Mr. exactly once. Every other situation involved at least one party with a PhD or MD and was Dr. and Dr. and Dr. and Mr/s.