I think you should prioritize what's important to you in anything 3DS related if it's true you haven't used your 2DS much. At the end of the day, New 3DS only has the C-stick and faster processing that differentiates it from other 3DS units. (I'm disregarding the design and larger screen, as we've already had different options for those features in the form of the 2DS and 3DS XL.) There are currently no New 3DS exclusive games announced outside of Japan, so there's no telling how quickly the games will get here. I'm expecting a late 2015 or early to mid 2016 release for the first New 3DS exclusive game in the West. Are you still going to be invested in all of this at that time?
I see that you have the demo of Super Smash Bros. for 3DS downloaded, but do you own the full game as well? That'd be one to take advantage of both the C-stick and faster processing, but if you don't play Smash Bros. on your 2DS, then are you really going to get much out of the Ambassador Edition New 3DS? I personally bought a 3DS XL just to play through all the Ace Attorney games and now that I've done that, I'm selling my 3DS XL and waiting for the next Ace Attorney to arrive. Whatever platform it'll be for (New 3DS, future 4DS, whatever) is going to be my next handheld console. Do you have any game or series like that, warranting a purchase of a console on its own? If not, I'd seriously reconsider putting your money aside for something you're probably not going to use much.
An Ambassador Edition New 3DS would make a very nice addition to a collection though, but apart from that purpose I'd say keep your 2DS and look into a New 3DS only if you feel it's worth it to you. At this point in time and likely one or two years later it's still going to be hard to justify upgrading to the New 3DS unless there are games you specifically want to play that take advantage of it / are exclusive to it. That's how I see this.
