Just my opinion: I don't feel that it should be completely replaced, but I think the idea that it's necessary needs to go. Tons of gyms out there still ONLY train gi, or they have only 1 or 2 no gi classes per week with a ton of gi classes. This should be flipped around. The gi simply doesn't represent the time we live in. If Judo and Jiu-Jitsu were invented in the past few years rather than generations ago, the gi would not even exist. It serves as a tradition, yet there are arguments out there that exist just to justify its continued relevancy such as the argument that training in the gi makes you "more technical." Perhaps we should tell wrestlers their skills aren't technical because their uniforms aren't heavy and cottony enough? But I still don't think it should be gone altogether. Partly because of the history, but also because the gi does provide an opportunity to learn to use heavier clothing agains an opponent. This should be considered an extra bonus, though, not the meat and potatoes of grappling. No gi, especially sub only, is the purest form of grappling that exists and hence I feel that should be the standard in training and competition.