You got it wrong, we should watch the hashpower and not the nodes:
https://coin.dance/blocksSegWit need 95% signalling while BU is the one that needs 75%.
That's already slightly wrong, BU have already stated they will use 51% if they feel they need to.
And Segwit activation is probably going to change too. It will just activate, period, between October 1st and November 15th, according to the new BIP149