-Gamefreak & Nintendo are not stupid, they know that a R/S/E remake is in high demand and will make a ton of money for both of them. The idea of a remake of arguably the best Pokemon games to ever be released will pull old fans back into the Pokemon series just as HG/SS did for many others, especially after some veterans of the series were turned off by the B/W series the return of Hoenn will be great!
-Gamefreak has stated that they do not have a particular pattern of release for their games, but I have noticed that 3 "main games" (i.e. R/B/Y, G/S/C, D/P/Pt etc.) and 2 remakes(i.e. FR/LG, HG/SS) are released each generation so all together its a total of 5 games Gamefreak develops each generation (after Gen. 2 obviously). Obviously only 2 "main games" have been released in Gen. 5 so we can expect at least another game before Gen. 6 starts. I have also noticed that each generation has a 3-4 life span, Generation 5 debuted in 2010 (2011 in NA/EU) so we can at least expect either Gray, B/W3, R/S remake or a completely new project by Summer 2014. I do not think Gamefreak will break the 5 game cycle. If there is a R/S remake, it will most likely be release around Q3 of 2013 considering the fact that they not spoken about it and they will want to reach the holiday shoppers. What's better than a R/S remake and a 3DS XL bundle for Christmas? Huge profit for Nintendo!
But who knows, we have no idea how long they have been developing the game and Spring/Summer releases are common.
-If a R/S remake is actually in the works it will inevitably be a 3DS game. With all of the hardware the 3DS offers we can expect something great! Hopefully Gamefreak will try to tweak the story R/S to be a little more mature and complex because it is so many possibilities concerning Team Magma & Aqua! It can easily be best Pokemon game ever! This series continues to get better and better as the years go by, always making a set forward so whatever Gamefreak releases this year whether it be a R/S remake, B/W3, Gray or a new project entirely I will be excited for it!!
Gamefreak does not develop the spin-offs so anything concerning those games have nothing to do with their usual projects.