If you search around the internet you'll find that material shortages are plaguing the completion of RVs. A/C units, water heaters, sofas, and other goods are trickling in to manufacturers and most have hundreds of nearly completed RVs sitting in lots waiting for completion and delivery.
I don't know how much you should trust your dealer's word about anything. But from how you describe it your dealer doesn't sound like he's checking with Winnebago and getting a complete delivery date from the factory. Sounds like he's just winging it.
I'm not saying your RV is delayed but until you know otherwise you shouldn't set your clock by the "should be here" response of the dealer.
This week is the worst for getting in touch with Winnebago as the Grand National Rally just started yesterday.