The other problem with re-running a tour very quick after would be how many of the original passengers would be able to make it. You'd have those who might be working or have other commitments, those travelling from a long way who couldn't afford to travel again (especially if short notice meant they couldn't take advantage of discounts), those who just couldn't get there (particularly if they had re-run it today, being a Sunday), those stopping overnight who wouldn't be able to get or afford accomodation at short notice etc etc. They would all rightly want their money back, so you could end up with the tour running half empty or worse, and possibly making a considerable loss, on top of the losses already made for cancelling the trip on Saturday (crew wages, likely food for the dining service, track access etc).
I had considered doing this tour, but had other commitments, so couldn't, and I'm glad I didn't now. I can't see this will be the end of 87s in the UK, afterall the ACLG I'm sure will want to fill in the gap in their collection, and they are very keen on having mainline certified locos (even the 89 looks like it will end up on the mainline again).