Hi guys, to answer some of your questions. If he stays at Wasps, he can play for the French team (no rule in France about the player's location). He has a huge weakness, he is not a 'JIFF' which means Joueur Issu de la Formation Française (player from a French academy). To be a JIFF, you don't have to be French, you just have to be playing in a French years for some years during your teenagehood.
Year after year, the French federation increases the JIFF number which has to be align both in the squad and on the field for each game. Hence, JIFF players are like gold. This is for example a reason why Toulon didn't make effort to keep Halfpenny, why Castres not sign again Spedding, or why Castres sold Mafi.
Why would Toulouse hire a French non-JIFF player who just play sometimes in Premiership?? They can have almost who they want. The play philosophy is far different. OK, Toulouse is the most English-like club, trying to play fast with a lot of balls coming to the wings. Nevertheless, this remains top14, the game where players only play rucks, scrums and 10000 TMO/match. Not really the profile for a young and dynamic player.
Finally, the info comes from the 'Midol' (shortname for Midi Olympique) which is a rugby tabloïd. They release 2 editions/week, so they have to find any rumour with buzz-titles. Actually this is just a rumour. Let's see if this will be true.