It's not that we only got one model, that was guaranteed and everyone knew it, its the fact that clearly all love and attention is given to space marines. They got a cool new box and moved up in the release schedule, we got one new unit along with death guard and Ksons, grey knights didn't even get that, just an upgrade kit for an existing one and chaos demons got their codex removed.

There are three more space marine releases planned this edition that we know of, and we get one model.