It's going to sell around 2M copies, probably, while not being all that expensive to make, relatively speaking. I see no problems. A lot of games would love to sell at that level. It's not going to sell like the main entries, of course, but no spin-off ever will. I guess they could fire a lot of their staff and just churn out main series releases, though I'd prefer to have them years apart.
As far as the ads, I don't really know. It's probably more of a small preliminary campaign to generate buzz and get people aware. They'll start up again closer to release.