I definitely like the looks, so my concerns at this point are weight and engine options. With a modern look like that, I wouldn't feel weird about having a V6 exhaust note, which is how I feel about the current Mustang body; it looks a little too muscular for its V6 exhaust note (obviously only applies to the V6 model). So I would be all set for a 2015 V6 and a Track Pack (if they offered it) would be my only option ordered. However, if they replace the 3.7L V6 with an EcoBoost 4-cyl, I might not be okay with that, since I want a little more "grunt" out the exhaust of a Mustang than a 4-cyl can give me.
On to weight; the 2013 V6 weighs 3,500lbs. I wonder how much they can drop it for the new model. Obviously 3,300lbs for the V6 would be great, but I wonder if it's even possible with today's standards. Either way, I think I would be satisfied with a Mustang that looks like the rendering above, with the current (or a slight bump in hp) V6 with the Track Pack weighing in at 3,300lbs.
The EcoBoost V6 replacing with N/A V6 wouldn't bother me as long as all the bugs are worked out of the EcoBoost motors. I have't done much research into it, but I remember hearing a few horror stories.