Not true. It's different code on top of segwit. The first attempt in btc1 (very recent) didn't even increased the size (because it changed the meaningless "base size" without touching the weight limit. As for the current code, I don't think it has been properly tested today, let alone "for mucj longer than 1 year.
Anyway, I said, one year from tested release. Segwitx2 hasn't been released, has it? If so, too late to discuss a bip imo, the bip may end up being different from what has been released due to feedback (unless it is ignored again, of course).