If anything, I'd say that Junichi Masuda's tweet confirms that the games are not currently in development. As I said in the thread discussing the Bulbapedia report on the tweet, if GameFreak were working on it at the moment, wouldn't they be sworn to secrecy until the games were ready to be formally announced?
EDIT: bluesun's translation of the tweet:
‘Thank you! Your thoughts have been recieved. R/S are a very important work for me too. I want to create something good. Thank you!!’.