No official dates given. It's not much but…
http://www.trmk.org/forums/showthread.php/21116-I-just-talked-to-Ed-Boon-personally-here-in-Las-Vegas-about-LAG
http://www.mortalkombatonline.com/content/forum/showmessage.cds?id=137716
To sum up:
-Ed and co. are aware of the lag issues, and are doing everything they can to patch it up. They confess that the PSN being down was never an issue as they would have released a patch to the 360 users while the PSN users were waiting (of course, PSN users would have it once the PSN was back).
-Skarlet should be expected within the next month.
-All characters will eventually recieve additional alternate costumes, apparently based off of their concept art (I used to have access to the concept art images, but that's gone now :sad:)
-I think it's obvious to say that a lot of Klassic costumes are on the way, since I'd assume they'd be selling the MK Klassic costumes you could have gotten before the game's release. Not to mention, the newly found Cyrax and Sektor costumes found by hackers.
Also, I'd take it with a grain of salt: Ed Boon is hyping E3 quite a bit. A lot of people are thinking he's going to mention either the sequel or a spin-off. I think his excitement is based far more off of the OTHER games coming out, but who knows.
Also, someone on Twitter asked about the possibility of an Ultimate Mortal Kombat. Ed said that he's not currently planning on it, but he did enjoy Super Street Fighter IV.
Too early to tell about the very distant future, but I think a lot of content are coming our way.
Also, deconfirmed DLC characters (from comments of Ed Boon on Twitter):
! Mavado, Li Mei, Kira, Havik (holy shit….), Fujin (double holy shit), and most importantly, no characters from Mortal Kombat: Special Force (aside from Jax or Sonya, but characters like Tremor or No Face are not having a sleep over.
Possible DLC:
! Skarlet (dur)
Kenshi (double dur)
Rain (Ed hasn't said anything denying him so far as DLC. In fact, someone cursed him out on Twitter for not including Rain, and he immediately said "ever heard of DLC?" Definitely happening.
Tanya (Ed hasn't said anything negative, and said one or two positive things that could mean she's in.
Sareena (Nothing negative or positive, but if anyone got in, Sareena's got a sure shot. Namely since Ed adores Mortal Kombat Mythologies: Sub-Zero, and Sareena is probably the most popular character from a spin-off game in this series.)
–- Update From New Post Merge ---
Seems the source I had was removed from the message board. Oh well.
In other news, I did the 2-Day-Online-Trial to try this online...
Me: "Oh...the lag can't be that bad.
gets beat by a Liu Kang who could barely string two moves together, let alone his fatality