I agree, that doesn't sound right. There are two things to look at, the manufacturing side and the trucking side. Trust me, if Marquis has your order in their plant, they know exactly what day your tub will be ready to ship. It sounds like you might have to call Marquis to get the straight scoop on that side of it but give your dealer the chance to get you the answer. It's a lot more work for the Marquis people to find your dealer's order when non-dealer people call. It could also be a sticky situation for the Marquis people if your dealer has some credit problems; more on that further down.
The trucking side could be the problem. I suspect that hot tubs don't move on a common carrier trucking company. They may well move via a gyppo (sp?) trucking company that moves a full truckload from point A to point B. They're a lot less money but you just can't call them up today and the truck will be there that afternoon. They are arranged via a truck broker whose job it is to get that truck another load as soon as it's empty and with as few deadhead (empty) miles as possible between deliveries. It may be that there really aren't any trucks currently in or near Independence, Oregon (where Marquis' factory is) willing to go to your area when their truckload is ready to go out. It may also be that Marquis doesn't have a full truckload, say only a half of one, going to your area and the broker can't find a load to fill the rest of the truck.
A third possibility could be that your dealer is having financial difficulties. This is the one you should worry about. If he hasn't paid for tubs already delivered to him, he may be on credit hold with Marquis. He is then forced to wait until someone else buys a tub from him so he'll have enough cash to pay for those previously sold tubs and Marquis will then release new orders (yours) to manufacturing. This is what happened to Dino; search this site for posts by Dino and Dinoguest. I still feel bad for what happened to him.
My suggestions are to one, call the dealer and have them call Marquis to see when it's going to be ready to ship. Don't ask when it's GOING to ship; you want to know when it WILL BE READY TO ship, i.e., when it's done being manufactured. THEN find out when will it be shipping. That part might be harder to figure out but not impossible.
Good luck!
Jim