The Gen III remake is a very controversial topic.
Many believe it will not be created, and many believe it will be - all for varied and respectable reasons. The main reason of why Gen I and Gen II were recreated was so you can have access to those games, and trade with them, since it wasn't possible due to the non-connectivity between the Game Boy Colour and the Game Boy Advance. Since now all five regions can join in the fun, it would be redundant to make a remake.
However, another theory is because of the poor quality of Gen I and Gen II, and now by comparison, Gen III. The DS's effects to the Pokemon series impacted Gen IV, with the psuedo-3D effects to the game. Now, with the Gen VI's 3D effects, if this is the case then expect a Gen IV remake.
The reason, really, is unknown since Game Freak hasn't confirmed anything at all.
So, just pray it will come. (Lol. xD)
Hope I helped. :)