If there didn’t seem to be any prospect of more Red & White REs after April 1978, then it must have been certain by the summer of 1987. But no, it wasn’t.
I will add more details about the general history of the company elsewhere on this site, but NWOS was financially challenged throughout it’s entire short existence. The eastern (English) part of the operations were separated and sold to Western Travel in 1991, along with the operations in the Gwent valleys, and the Red & White name applied to all of these operations. In 1992 the remaining part of National Welsh was declared bankrupt, and the recently formed Red & White expanded westwards by acquiring the former NW operations in Aberdare, which had by then been merged with the former Cynon Valley DC operations. Cynon Valley, in its previous form as Aberdare UDC, had purchased two batches of 7 and 6 Bristol RESL6L/ECW buses in 1972 and 1974/5 respectively. These had proved to be economical and reliable, useful characteristics in the deregulated era of the late 1980s, and three of these vehicles were still in the operational fleet at the time of the Red & White takeover in 1992. At least some of these received a white based livery with red and grey stripes, and Red & White fleetnames. The livery was again short-lived as by the end of 1993 the company had again changed hands, this time joining the Stagecoach empire.
The surviving operational REs received Stagecoach corporate livery, and remained in service for a couple of years. Stagecoach also retained the Red & White name as a subsidiary fleetname at this stage, and one of the ex-CV REs has also survived into preservation.
Thus there have been Red & White REs in service, spread over the best part of thirty years – a good record, even if another revival really is out of the question by now!