I believe they've said they do not wish to bring it back into player gameplay unless they can provide it with the weight they feel it should have as reflected by the lore and attitudes towards it.
Indeed so. Blood magic has great potential as a story element, but in order to fulfil that potential, it can't be limited to a combat school. Blood magic options must be present in many encounters - for mind control, for sacrificing a companion for power in order to win a boss encounter by default, for casting powerful magic with your own blood when deprived of any regular power source, and similar things - in order to come across convincingly, and the world must react plausibly to its use, and to the way its used. Making all that is problematic resource-wise because it'd be exclusive to mageborn protagonists.
Thus, we'll only see it if blood magic is an important theme of the story. It may require that the protagonist is canonically mageborn (though not necessarily a mage, just with enough training that he can get by doing warrior or rogue things without the magic getting in the way). I think it can be done with a plot set in Tevinter, and I hope they want to do it and manage to pull it off, but maybe they'll have a different story in mind, and if don't see blood magic therein, that's ok, too. I'd rather not see it at all than implemented cheaply.
If they choose to do it, they could do worse than to look at the Minecraft mod "Blood Magic" for inspiration. Therein, you accumulate power to fuel spells and devices by storing life essence in a gem. You *can* get by using only your own life force which regenerates over time, and there are rituals to make that more efficient, but in the end you'll get drastically more power by killing stuff. When I played it, I was reminded of Dragon Age and thought: "If you want to show the temptation of blood sacrifice, here you have it." Blood sacrifice must have significant, even drastic benefits over the alternative, or nobody would bother with the risk of murder.