A place like IKEA should be an additional attraction to lure visitors. People drive long distances to shop at those stores, and they often spend big bucks while they're there, not to mention spending at other nearby stores and restaurants.
As for an IKEA locating near a downtown core, I'm not sure how common that is, but they had broken ground on one in Tampa just as I was moving from there 6 years ago. The location was very near residential, adjacent to a busy cross-town highway, and within a mile of downtown, the Channelside port district and the Ybor City district, all tourist spots. A North Gulch area would seem very similar in the type of location with its proximity to tourist destinations.
The Tampa IKEA site before construction: