I think everyone would agree that MHP3G on PSP would've sold significantly more than MH3G has on 3DS. However as charlequin laid out so thoroughly months ago, Capcom had to start transitioning the userbase eventually, and the longer they waited, the longer the uncertainty of which direction (Vita or 3DS) the fanbase should go. Capcom needed to set a clear direction early to avoid any unintentional userbase splits while they kept mum on the direction for the next game. They effectively sacrificed short-term sales in a 3G game in order to have a firmer foundation when 4 comes out.
I don't think 3G ever would have existed as anything other than a transition title, so I'm not even sure dubbing it a sacrifice is accurate.