nobody can answer you as nobody has heard the M project, so we are all speculating. My personal take is that the M project will be great, but Q7 will remain the best Magico speaker for a while (not talking about Ultimate)... and actually the best electrodynamic speaker on the market. I see the M project as an exclusive offer (production limited to 50 pairs), in a nicer package than Q7 (smaller footprint, rounder form, carbon sides), delivering 90% of Q7 sound for two third of the price. I see the market for that.
But if you can afford the Q7 (both money wise and in term of room), I would go for it. Nothing under 400k beats it.