Trump's just going to lie and say he won and that "the wall" is getting built, no matter what the bill says. He's already convinced his idiotic supporters that construction on "the wall" is well underway -- hence the banners at his rally that say "finish the wall."
I think Trump knows full well he's never going to get anything like the continuous 30' concrete and/or steel wall that he sold to his xenophobic base. Not even close. But getting it isn't really the point. The point is whipping the xenophobic base into a frenzy of fear, hatred, and authoritarian followership.
The sweet spot for Trump's appeals to the xenophobic base is a kind of balance point between "the borders are wide-open, we're all in terrible danger, the barbarian hordes are rapidly approaching" and "but The Wall is getting built, very, very rapidly, we're winning, we just need to keep it up."
So while the shutdown does inevitably take the form of hostage-taking, the underlying crime Trump is pursuing is more like the Long Con.