I don't think that there is a universal answer. LH, AF, BA, LX, SQ, CX, EK .. still have a true long haul 1st class product and make money.

OS, SK, KL, AZ have abandoned 1st class. CO without F is better off than AA or UA ( for me the latter 2 are not qualifying as quality carriers )

Question is if the Netjet type business case is sound for medium haul continental travel and leaving a 1st class niche for long haul intecontinental. It will be interesting to see the result of the LH private jet program, which tends to combine the two.
So far most LH private bookings were point to point with only few connecting to LH long haul.
Main variable are the travel policies of the big corporations, how far down the ladder can you travel in F or C? I started mid 90ties with a Fortune 500 US and had 1st class privileges. Around 2000 they cut it back to Y for all employees for intracontinental travel ( yes also on the red eyes to the East coast ). My successor can only fly in C on flights over 10 hours, otherwise its Y for all employees, which is tracked by an elaborate internet based travel expense tracking system ( with a monthly deviation reporting ).