In my view, the most recent iterations of the NHL series have been a bit disappointing with usually one new gimmicky feature each year which "will revolutionise the way you play the game". Although the game has improved somewhat each year, I haven't bothered buying a copy since NHL 09 because the single player has never really felt that different. A large portion of the development has been in the mutliplayer aspect of the game.
Will this year be any different? Maybe...
Producer Sean Ramjagsingh recently said that the developers are looking to dispel the general view that the game's AI has been underdeveloped. NHL 13 will see the introduction of what they're calling EA Sports Hockey IQ. According to EA Sports, they have spent more time developing the AI in NHL 13 than the past three years combined. Examples of this improved AI, or Hockey IQ (to use its fancy name), include better goalie awareness (particularly during odd man rushes), improved team mate AI (e.g. if you cross over into their lane, they will know that they should criss cross and position themselves for a scoring opportunity), and better player differentiation on the ice (e.g. the fourth line will play more aggressively in the corners and finish their checks). There will also be improved and more realistic tactical options. This all sounds quite promising. If it lives up to its promise then it may well make a big difference to the single player game.
The most hyped feature for this year is most probably the True Performance Skating. According to a study by EA Sports, players in the NHL glide nearly 40% of the time. In contrast, players in NHL 2012 glided less than 1% of the time! EA Sports is looking to make the skating more realistic and also prevent forwards from being able to unrealistically skate rings around the defence. Additionally, players will fatigue more quickly/realistically. Whilst on the topic of defence, apparently defencemen will no longer be successful when "poke check spamming". With regards to the offence, apparently it will be much harder to shoot accurately when skating fast. This all sounds rather good - assuming of course that EA Sports actually delivers what it says.
Another area undergoing overhaul is the Be A GM mode. The trade AI is being targeted in particular (EA Sports has dubbed it the GM Brain AI - did it really need a name?!).
As for new features other than gameplay, there is going to be an NHL Moments Live feature allowing you to play "memorable moments" from the 2011/12 season (maybe the Bruins v Canucks game from earlier this year?!

With the exception of the Be A GM mode (which is both single and multiplayer), there hasn't been much news with regards to the multiplayer game. As far as I'm concerned, this is really great news. All things being well, this year's iteration could be a big step forward for the franchise...