I would hope the Democrats would restore the pay-as-you-go (PAYGO) rules they have been campaigning on:
If you want more tax cuts you have to pay for them. If you want new mandatory spending you have to pay for it. If you do not pay for it, you have to muster a supermajority vote on the floor of the House/Senate for more tax cuts or new mandatory spending.
We'll see if that happens.