Funny you mention it bc I was thinking the exact same, just hadn't brought it up yet. Frankly, bc I'm not qualified or experienced enough to justify my opinion. That said, I bet integrated stems and bars could become standard, and may actually be stronger/superior to the current norm. Especially since carbon stems are already commonplace. Although, I will say that the Easton Haven 75mm stem and Haven 711mm bar is one of my favorite parts of my bike. Just looks beefy and bad ass. Not sure I'd want to switch to an integrated option like the above but if it was proven to be stronger and lighter. Especially for the price.
Basically, If they'd make one that mimicked my set-up (bar rise, bar sweep, similar beefy stem structure and design) and it was stronger and lighter... would be a no-brainer. Not sure if the stronger part is even possible, though. Like I said... not an engineer or carbon expert.