Source: nintendoeverythingGame Freak designer Shigeki Morimoto recently issued a letter on the Pokemon Global Link. In it, he left a tease about the newly announced Pokemon Omega Ruby and Pokemon Alpha Sapphire games. The two remakes, he believes, will offer a change in the generation VI battle environment.
Source: SerebiiA new trademark has been discovered as being registered by Nintendo, GameFreak and Creatures Inc. in Japan. This trademark is for デルタエメラルド Delta Emerald. In addition to this, in the US, at the same time as the Pokémon Omega Ruby & Alpha Sapphire domains were registered, one was registered for Pokémon Delta Emerald. This trademark registration is not likely to be indicative of a game release, but rather covering bases in a similar manner to the registration of Pokémon WaterBlue back in 2004 and numerous other Pokémon names over the past 10 years including Pokémon Grey. We'll bring more as it comes
With this games we have now gone full circle. Chronologically speaking the next remake would have to be FireRed's and LeafGreen's since those games came before Diamond and Pearl. So after this it would be the prefect time for Nintendo to finally remake Yellow.
I think it would be more likely to be Blue, if they did do it, since that was the proper "third" version for Gen 1. Yellow was a Special Edition intended to draw in fans of the anime, and while that's still popular, it really isn't as significant these days.