Socata is alive and well and selling about 60 TBMs a year - that is about $200M a year. More than the combined "GA" revenue of most names in GA. They support the TB piston range (mfg stopped 2002) and I gather they fully support the Rallye range (mfg stopped in the 1980s) with parts.
IO540 - I think you'll find that it's difficult to obtain support and parts for the Rallye from Socata (although they claim otherwise) and the company with the distribution rights for TB range in the UK has gone into administration.
Air Touring Ltd enters administration - Business & GA Forum - AirSpace