Contrary to popular belief on this board, 800 was not the primary cause of the 747's demise (and for that matter the L-1011 and 727) at TW. All three were on their way out.
By mid-'96 virtually all of TW's 741s had reached the 100,000 hour mark. (800's N93119 was the baby of the bunch with 93,000+ when she was lost) They were quite simply wearing out. The L-1011s were being dumped at that time for the same reasons everyone else was dumping them. (high fuel consumption; maintenance and spares costs) The 727-100s were long gone ('93) and the oldest -200s in the fleet ('68-'70) were mostly gone.
With TW's gradual withdrawal from Europe and the Middle East and 757s and MD-80s on order to replace the L10s and 727s on domestic routes, The days of all three were numbered at the time of 800. The public perception caused by the usual post-crash media frenzy did accelerate the 747 retirement a bit.
As for seeing any more 747-131s being turned into freighters, forget it. Those birds are part of an exclusive (for the time being) club having reached the 100,000 hour mark. To my knowledge AF and BA are the only other airlines to have put over 100K on a 747. KLM and Swissair have both done it with DC-10s. All told there are probably fewer than 25 airframes of all types that have flown over 100,000 hours. When they're retired, nobody wants them.