Apparently, a program like Today Tonight costs $17 Million a year to produce if a report (Sydney Confidential, so take it with a grain of salt) I read a while back is to be trusted. Not to mention that most of the old East Coast-based Today Tonight team has either since left the network or been redeployed into other roles such as news.
I'd imagine that if TT East Coast was really returning, by now we would've seen a huge promotional push and announcements of a presenter and new reporters. It's been nearly two years, the former TT audience has undoubtedly moved on to alternatives (or switched to ACA! ) by now.
Perhaps at some point in the future, Seven might revisit the concept of a nightly current/public affairs program but right now I think that Seven's main focus would be on preparing for relaunches of Sunrise and (more than likely) the news as the Martin Place studios currently go under what is quite possibly their biggest transformation since the move in 2004.