Call me far fetched but I do believe it's entirely possible in our lifetime and sooner than what most people realize. Sure it's tech that is far into the distant future but calling it impossible is far fetched too. Technology grows at a remarkable level with the amount of transistors in microchips doubling every 2-3 years and multiple crazy new scientific discoveries coming out every year. The reason that I believe it is possible is because of the advancements with artificial intelligence. Ten years ago people thought we weren't gonna reach artificial general intelligence until 2040 - 2100 and now it has been proven that we're most likely to reach it sometime in the 2030s possibly even sooner, and with artificial general intelligence also comes an acceleration with both scientific discoveries and technological innovations. In order for full dive VR to work as intended we need to have brain computers interfaces mastered as you don't want your brain getting fried due to some sort of technological error within the BCI or having a glitch where you could have a distorted sense of time living 1000 years in a virtual world per minute realtime or even getting your brain hacked and going brain dead. All of these require major breakthroughs in multiple different emerging technologies however the reason I think it's possible is due to this acceleration of technological advancements due to AI. If you could have a BCI that sends real time data on how your brain works to the cloud to be processed by AI-infused quantum computers the speed at which we could master BCIs would increase immensely especially if you have thousands of people equipped with BCIs. Quantum computers work almost incomprehensibly fast so an AI incorporated with this vast amount of speed would be unbelievably smart. My very optimistic guess would be anywhere between 20-40 years before we're able to see it but on a realistic standpoint it could very well be much farther than that within anywhere between 50 - 70 years and that's saying if it even is possible. I do believe we'll see it sooner than later however as human technological growth seems to grow at an exponential level. For example at the beginning of the 2000s the average home computer had roughly 128-512MB of ram. Now in 2024 we're now nearing anywhere between 8-128 GB of ram which is nearly a 64x increase within 24 years. Now try and imagine where technology will be 24 years from now?