Wormy,
I shot a 7mm TCU in steel silhouette competitions for many years out of a 10" Thompson Contender single shot pistol. I was able to hit rams all day long with open sights at 200 meters. As far as i can tell the 7mm TCU and 300BLK are identical as far as down range performance. Seeing how that round drops steel at 200 meters, i dont think i would feel comfortable taking a shot on a deer much past 100 meters unless i knew damn well i could hit a perfect vitals shot. It is a cool round, and i am sure it is fun but i dont think it is the best hunting round at any type of range at all. I have read the same as you that they are coming out with all kinds of new ammo for it, but the biggest problem is bullet design. Unless they start coming out with .30 cal bullets that will honestly expand properly at 1250-1500 fps then i would look elsewhere for a hunting round. 100 meters and closer i think it would be great, but man there are a lot of other options at that range.
458 SOCOM looks like a shitload of fun to me at 100yds on just about anything =)
IMO, a 300BLK is perfect for a supressed SBR at close/mid ranges, but it falls on its face when you try to stretch its legs so to speak.