I, personally, wouldn't send anything to ETI until they ask for it. They will have another building, but it's gonna be a while as it wasn't very far along when I was there a few weeks ago. I think I just saw a bit of rebar sticking up out of the ground or some such. Definitely not any walls.
I don't know how they handle storage, but I imagine they wouldn't want tons of stuff sitting around for months on end.
For flooring, you can order from Pioneer Building Supply and they'll hold on to it for you. Jackie (the gal that orders flooring) said they're well used to holding on to flooring for months on end, until ETI needs it - good thing as ours has been there since Feb or so. By ordering now you won't have to worry about the supplier being out of stock for when you do need it, nor do you need to worry about it being discontinued when you do go to order.
For fabric - that stuff can hang around your house until you need to ship/deliver it to them. Mine has been hanging out in the attic for something like 7 months, at least. And will be for at least a few more months, until they need it.
Yeah, you may need to pay double shipping (to you and then to them), but at least that way you know you'll have what you want, in case it does get discontinued.
As already mentioned, asking ETI is the best. But I wouldn't worry about sending stuff this early, when your delivery date is next April (I think that's what the OP said; going off memory here). Why risk it getting lost or damaged or whatever during all that time. Just start a box or whatever at home and start stashing stuff in there. We won't mention how much of our attic has stuff stashed away for ETI and for when we actually get The Trailer.