My opinion, and I repeat this is only my opinion POGS (though there is the evidence out there to suggest this might be the case) is that the PLP will unite behind Corbyn, with a few exceptions.
I accept that as a long-time pacifist (as I am too) and a member of CND (I marched in my time) and a holder of a prestigious peace award Corbyn has views which some might consider different. As a back bencher he upheld his views and principles.
Now, however, he is the leader of the Labour Party and has another strongly held principle to uphold, that of democracy. I genuinely feel that this man, while still having strong anti-nuclear and pacifist views, recognises that as Leader the will of the majority within his party, democratically elected, is reflected in The Labour manifesto. And as a man of principle he will bow to the god of democracy.