If Corbyn wins with the NEC onside, the PLP have three options, work with the Party (because its the Party they're fighting), leave, be de-selected. The Party has had enough of them, if anything Corbyn has held the constituency parties back, he genuinely wants to work with the PLP, there's many a constituency party that wants their MP gone.
If the Blairites don't like it and they point to their mandate from electorate, great, stand as an independent, they've been squatting in Labour's house for too long.
Its the "work with the party" option that I don't really get. I don't see how that that's possible during a general election campaign, when so many MPs clearly do not support the leadership. Even if they adopted the lowest possible profile, the campaign would end up descending into farce.
In practical terms there are only really the two options. Once Corbyn wins the leadership election contest, the rebels need to form their own party. Or Corbyn and his supporters need to oust them.