The rules let you get the tax credit as a rebate when the upgrade is done, though I don't think that has fully rolled out.
The reality is that in much (though not all) of the country, it's cost-effective to replace a near-end-of-life fossil furnace with a heat pump, since it will lower their ongoing heating bill. People do still need to substitute capital for future fuel payments, and that's a big deal, but it's a lot better than it was.