It's difficult to say how much % the chance is for the hard fork to really happen, but the chances for it not to happen are higher (thus over 50%). My personal thought regarding the BU threat is that they are just trying to put a huge load of pressure on the Core side to come up with an 'improved' solution. Mining operations are just in the game to generate as many profits as possible, and thus won't put their entire operations into danger by forcing through a hard fork that will result in a huge short term blood bath. But then there is also a possiblity of a 'hostile takeover' in the way that they will just take the risk and let the fork happen, in the hope that the support will then shift to BU where entities as Roger Ver and Jihan Wu will be one of the main players (i.e. hunger for control). Time will tell whether or not BU is just barking, or they really plan to go through with their hidden agenda plans.

Interesting site that shows how much blocks have been mined with what sort of signalled support; https://coin.dance/blocks

Signalling support is nothing more than pools letting know what they support through the Core client. Don't directly add too much value to the numbers shown. It's just an indication tool rather than something decisive.