Right... which makes it not so exclusive. The digital upgrade almost certainly won't cost 70 USD ($20 tops would be my guess), the price will go down over time, and some (if not all) the digital goodies will eventually be released individually on the ESO store. In fact, I expect the Imperial race will be the first thing in the pack to be sold as an individual item, and I'd expect that to happen within six months.
Hasn't seemed to stop other MMO companies from doing so. There's an MMO out there that now lets you buy a "Founders pack" full of goodies that were originally advertised as pre-order exclusives. You even get a Founder title to show off your newly purchased pre-launch devotion!
The physical swag will stay exclusive (aside maybe from promotional stuff at conventions), and I can see buying Imp for that. The digital stuff... well, if there's demand for it, it will somehow make its way into the store.