If it was invasive (and possibly fast) I could potentially see a technology similar to this being approved for clinical use, such as in a hospital. If someone is in a coma, for example, there might be a possibility of hooking them up into this machine quickly enough before their brain completely goes into stasis where they would be able to almost see through a screen into the outside world and control a sort of body, it would be on wheels though. They could choose when they want to see in and out of the real world, in between being able to adventure/play around in a virtual world. It is an interesting concept, I believe. Of course, this would then allow the person in said coma/stasis to interact with the world still and possibly make it easier to monitor their brains to make sure they are not being damaged. Just a thought.
Also, TheOriginalKirito, "If I find more I will edit the post." You are essentially saying you researched some of this, not that you are an expert on MMO Games. Yes, there was a good estimate by scientists that by the year 2020-2025 we will probably have photo-realistic graphics. That does not mean we will have mapped the billions of neurons inside the brain or exactly how they operate either. Both are necessary in order to achieve such technology as we are discussing. And also, there is always a safe way to do something- there are millions of ways to do specific things, there are only just a few we can think about at the same time. Eventually there will be a time in the future where we will most likely have mapped the human brain and be able to use it where it could "transport" of sorts you to another world. However, the technology would also have to be designed to a point where the game/world could not take complete control of the person's brain, such as it does in Sword Art Online. However, a circumstance in which a scenario is built into the software where it would take control of the player's brain would probably be found by whoever was approving (whether it be a patent office, the government, etc.) It is extremely unlikely that a scenario such as Sword Art Online would actually occur.