It all depends on what happens when Congress tries to raise the debt ceiling. Despite protestations from the Obama administration, Republicans insist they're not going to raise the debt limit without extracting severe spending concessions from Democrats. Indeed, they say that Republicans won't vote to raise the debt limit without such concessions.
But every member of leadership in both parties, and everyone at the White House, knows the debt limit will be raised one way or another. It has to be. Therein lies the key for Pelosi.
Right now, House Democrats are coalescing around the view that the debt limit should be hiked without major concessions to the GOP attached to it. They want a "clean" increase in the debt ceiling. If House Democrats hold to that position, they'll force House Republicans to pass a debt limit hike with only Republican votes. What the conservative base of the party would demand under those circumstances is unclear, but there's a high likelihood it would reach way too far, and be a non-starter in the Senate and with the White House.
That's where Boehner would get stuck. He knows the debt limit needs to be lifted. He knows that to get a debt limit bill through the Senate, he needs Democratic buy in. And if Pelosi and her leadership team keep Democrats aligned, he knows that means ditching just about all the concessions Republicans want.
Boehner would thus be forced to lift the debt ceiling on Pelosi's terms, not his own. It would make the defections he suffered during the 2011 spending fight look like a minor rift. But he'd have no choice.