Well, new costumes are great, because ever MK brings characters with new look.
But even if their costumes will be from old games, I still like it. That is the way they are now.

well i hope they get 1 new costume

Actually, the video on IGN.com shows Reptile in both his MKDA and MKSM costumes. When it shows a long list of Renders, its his MKSM form. But in the Intro video, we can barely see him running in the background in something like his MKDA form. I was expecting this because of the Character Wallpaper had a new reptile render reminiscent of his old MKDA costume.

i hope they get 1 new costume at least

I agree. While I love most of the MKDA-MKD costumes, I still think new ones would be great.

Yeah, at least one new costume should be added. Maybe they could make them unlockables only these would be things we wouldn't know about and they'd be in the game to surprise us.

I agree they'll have 1 or 2 costumes per character. I hope they'll have 3. They've had time to work on the new characters a lot, and perhaps, if they change them, they will do so in the final version. This teaser was about seeing all the characters back in action, so, in a way, it makes sense to display them in their most recent, familiar garb.
I was going to post that Reptil had two costumes, MKSM and MKDA, but you guys are all over this like mice on cheese. Pretty fun. I don't need to see any more info, spoilers or the like. I'll wait until October.

Definitely agree that everyone returning should have at least one new costume. Those returning from shaolin monks should carry those costumes as alternates for the new costumes.
-Sub-zero has his armor again from Deception which is great because that's my favorite costume, but like I said his alternate should be his shaolin monks attire for ex.