What the heck are you smoking?
The purpose of FR/LG is not just to let R/S/E have Johto and Kanto Pokemon.
Remakes of RBY and GSC have been requested by the people, and They have heard our cries. Adding Johto Pokemon was just an extra.
Making TY would not be a waste of time or money either. Chances are, if TY gets released it will sell better than FR/LG or R/S/E.
Also, They have made 3 for every set now. RBY GSC RSE and now FR/LG. Can't you take a hint?
Also, making 3 games is a great marketing idea. When the first two come out, some people will buy both versions to 'catch 'em all'
Then they come with a Third that has extra features and everyone buys that game also, but they reduce the amount of Pokemon in it so that you must trade with both FR and LG to catch them all. But in this case, you must trade with R/S/E FR/LG/TY to catch them all. Ingenius.