Hm? I always thought R/S and B/W took place during the same time. Strange.This could only work if said games were sequels to R/S instead of just remakes. Ruby/Sapphire take place at the same time as Red/Blue. Because of this, Ruby/Sapphire take place three years before Gold/Silver, and there is evidence in Black1/White1 that Black1/White1 take place some time after Gold/Silver.
Having this cameo in R/S remakes instead of sequels will cause problems with the timeline, unless Game Freak is willing to ruin the timeline, which I doubt they'd do.