India will not join any foreign program. Honestly apart from the engine when it comes to the plane the French have a much better fifth gen program. Since Germany would be with the French scaf it will be a bigger export success than the tempest. Plus scaf also will have a naval variant. That isn't case with the tempest...
The French program is at a higher risk of failing because they have very dubious partners. Both Spain and Germany are the least trusted amongst the EFT partners. And Germany will be the biggest political hurdle when it comes to exports, they don't like exporting weapons to countries that have a high possibility of going to war. Also, both Germany and Spain are incompetent, they do not have anything significant to offer, and if they do end up contributing to the aircraft, then the FCAS will be all the worse for it.
Britain has the best partners, particularly Sweden, although even Sweden has issues selling jets to some questionable countries, including those that can potentially go to war. But both Italy and Sweden have accomplished aerospace industries.