There you go, figure 6" in 1 1/2 years. Remember they grow faster when small and then continue slowly. Any bigger than this and the tank will start getting small but that is still a long time. If you are thinking about upgrading now, you will either do it or start losing interest by them. Either way, based on your concerns about adding this fish, sounds like you will be getting it a new home.
I'm curious how long it took the fish to get this big in a 210.
Greg1786, my feeling is that you are a conscientious aquarist and want to get this fish otherwise you would not have started this thread. You will always get someone to say go for it and someone to say you cannot do it. Fish are confined no matter how big the tank, the only question is at which point does it constitute abuse. For example, Rea17 thinks a 520 will not be big enough for a growing Sailfin and I personnaly disagree. End of the day, Rea17 got to enjoy the fish for a considerable period of time and I'm sure the fish was fine. All I'm saying is not to deny yourself the pleasure as long as you can do it with a clear conscience.