I don't think I've ever seen an explanation of the "lifetime deal", and whether it really means C5 are obliged to buy the show for as long as 7 want to produce it. Even if that was the deal, I'm sure it could be renegotiated. It is strange though that C5 gave up on Neighbours, but continued on with H&A, when it was less popular.
I can't see how axing H&A from the main channel can be a good thing, but perhaps figures for the lunchtime slot were so low that the number watching on 5Star or On Demand are enough to make it profitable. As they're still buying the show, I don't know how dropping it from the main channel could save them any money, unless they think it will drive more viewers to the On Demand service, which I assume they make a profit from through advertising. H&A must cost C5 less than what it makes in advertising revenue. If it was losing them money (as they said Neighbours was, if I remember correctly) then surely they would look for a way out of the contract ASAP.
The beginning of the end? Hard to know. It does push H&A further out of the mainstream. If this change means that total viewing figures fall, I could see that as leverage to negotiate a cheaper contract. I'm sure H&A will continue for a few more years at least, as no doubt they'll want to celebrate the 40th anniversary in 2028, and surpass Neighbours in terms of longevity. Having said that, for some reason H&A doesn't seem to celebrate milestones any more.