I have an odd feeling that D/P will have some sort of connection to Johto. I hope, Johto has been shuned into the corner.
I doubt that there will be a Lightning Yellow, i mean, FireRed and LeafGreen came out for ether two reasons.
1.The people at Gamefreak felt bad for their mistake in R/S. Notice the old pokemon in E.
2. They are wanting to drum up suspence over D/P. The makers combined Emeralds Battle Frontier by having Ash go back to Kanto(FRLG) though battling the Frontier Brains. (Emerald)
Afterword, D/P will be realeased. Their doing what they did after Kanto, the Orange Islands. Their doing the same thing.
Note:You guys got your answer to Orange Islands, Sevii Islands.
So, long story short, no, I doubt they will make a lightning yellow. It would be
neat and hot if they did, but, i doubt it.
I still think the makers have this all planed out. They probably already have the 5th generations made.
As always, be kind to the mime.