The current BBMF inventory will not remain flying for ever
Why not?
The types currently operated have been frequently resurrected from nothing much more than the manufacturer's plate. They are all constructed in a relatively simple way using basic engineering and readily available materials and technology. Perhaps the Hurricane with some wood and fabric poses the biggest difficulty because these skills are almost dead.
Given the will to keep these prominent types going the cost is well within the realms of purely public subscription. The addition of fuel-hungry relatively modern heavy metal with more expensive technology would raise this cost to the unsustainable.
I congratulate those who got the Vulcan back into the air and I hope they can keep it flying; however, I would not like to see that endeavour jeopardise the future of BBMF as we know and love it.