It's clear that, at the time of the interview, they wanted more than 2.7 million sales for DmC. It may be 3.5m, 4m, 4.5m or possibly even 5m. However, they have never explicitly said what they were aiming for. They could very well have aimed for 5m but claiming that they were targeting 5m(even when he mentioned 4m as well) from the get go without evidence is pure conjecture.Boosting sales means targeting that 5 million. It was pointless for them to reboot just to get a little over a 3 million sales which is what DMC4 already achieved.
They saw God of War selling 5 million and wanted a piece of that pie. The intentions were pretty clear by Capcom.