May I ask who your dealer is in NC? It is strange that they stated they were just placing orders now, because as you said, orders should have already been placed for the year. If I were you, I'd ask them to clarify what they meant by that.
A few thoughts regarding the SX210 at Wonderland...
1) Do you really want an SX210 or would you prefer to have the AR210 with the tower. If you want an AR210, I wouldn't settle for something different (at least not this early in the model year when there's a high likelihood you'll get what you want).
2) Are you concerned with the estimated arrival date your NC dealer gave you? While the SX210 may be available now, there's not much boating season left in NC anyway (depending on where you are in the state, of course, and how tolerant you are to be out boating in cold weather). I live in the Raleigh area and we'll probably be done for the season by mid-October (and by the last trip or two my kids will be complaining!).
3) I assume the $1400 for freight and prep is less than your dealer quoted, but is it so much less that you save serious money by driving all the way to Michigan and back? I know my NC dealer (Chatlee) charges like $2100 or $2200 freight and prep. Saving $700-$800 wouldn't be enough to make me drive to Michigan and back for a boat.
4) Lastly, remember there is value in having a relationship with your local dealer. If you cancel you order with the NC dealer and buy a boat from somewhere else, then show up at their shop with a warranty issue or something you are less likely to get any kind of preferential treatment at all.
If you have serious concerns that your dealer won't be able to deliver your boat as promised, then I agree it makes sense to consider alternatives. But if they just said something that sounds strange to you, or they happen to be a few hundred bucks more expensive than some other dealer halfway across the country, I'd stick with the order at the local dealer if I were you. Either way, good luck and hopefully it all works out well.