Why canceling the halving, i think it is programmed on that way that when the next 210,000 blocks are reached (on this halving it will happen on the 420,000th block), miners can not decide to approve or vote to cancel or not the halving. Let's see what will happen in less than 2 days.
Technically they can (if the majority wants to). On the other hand, they will never do something that would destroy their business. So, don't worry!
I'm sure that at least the canceling of halving is not going to happen in the next two days, but if they have the power it does not mean that they should cancel this. But if they cancel what will happen next? Will the next halving be 12.5 or less than that!! I understand the miners, they would be happy if this will happen!