No, it shouldn't. One, having it in CityWalk ensures that everyone can visit the preview center and see that it exists. People who're just going to the Studios can see it, people who're just going to IOA can see it, and people who're just going to CityWalk can see it. If it's inside just one park, that cuts down the number of folks who can see it and that's probably something Universal doesn't want. The more people that know the park is coming (and more importantly it's a separate park south of the main property), the better.
Secondly, the preview center is most likely gonna' be up for a while, at least right before the park officially opens. Operations will most likely want Mummy's extended queue for the busy Summer season, and then HHN will certainly need that space for the tribute store as HW's space just isn't big enough for that one.