Looks like you won't be seeing double.
An aspect that fighting games tend to stray away from nowadays are character duplicates and understandably so. Most gaming companies such as Capcom and Namco Bandai do this to avoid balance issues. Imagine playing Marvel vs. Capcom 2 (MvC2) online and running into three Cables.
According to Tekken Tag Tournament 2 (TTT2) producer, Katsuhiro Harada, developers were entertaining the idea of allowing players to pick the same characters on their team in 2v2 battles. That idea was quickly phased out once testing began.
See what Harada had to say to 4Gamer (via SGCafe) below:
“We tried this out, and it turned out to be extremely discomforting! (Laughs) For instance, if Lili were to launch her opponent and tag out, in comes Lili again… what the?! (Laughs) Also, suppose all four characters on both teams were Lili, we don’t even know what’s going to happen anymore.
To be sure, we had a bunch of test players come in to give this [duplicate characters on a team] a go. The feedback received was unanimous: ‘this is just not very fun,’ so we had them try 1v1 instead. As this format was pretty similar to past Tekken games, naturally it played well.”