It's a small part of a much bigger and rather important spending bill, so chances are it will be signed. That said, I agree that one should be 100% certain that it's been enacted into law before making decisions based on this tax credit.
FWIW, a similar credit was in place when I had my Clipper Creek HCS-40 installed in 2016 for the Chevy Volt I was driving at the time. My biggest recollection about the credit is that the tax software I used for that year (H&R Block; I don't recall which variant) did not include the necessary form. That was a royal pain; I had to fill out the form manually from a PDF provided by the IRS, enter an override into the main 1040 form, print everything out, and file both Federal and state taxes via snail-mail rather than electronically. A friend of mine who used TurboTax that year and who had also installed an EVSE did not have this problem. Thus, I recommend you check to see if your tax software supports the form in question before buying the software (assuming you use tax software, of course). With any luck H&R Block supports the form by now, but I have no definite knowledge one way or the other. You might also want to avoid filing at the last minute, just in case you need to jump through the snail-mail hoop.