At this point in time, I cannot see BU being activated or SegWit for that matter.
I think BU would mostly happen cos its like an altcoin, you just fork it. Just like ETC
BU will be no help to Bitcoin. You see what happen to ETH hardfork and now no one cares about ETC, as only the ETH rules. Same way BU will be treated and BTC cant be replaced, not by the BU even.