I think those forecasts were realistic when they were made. Inflation has clearly been stable since they were established and published. If private sector forecasters redid them today, the $41 billion amount would very likely be revised upward since there's no indication inflation will abate.
As for the other question on the impact of sustained inflation, prices are obviously rising, but I imagine you're mainly referring to the effect that would have on public finances. Since the federal government charges roughly 14% or 15% of GDP in direct and indirect taxes, its spending will also rise slightly under higher inflation to offset the increasing cost of certain benefits and the goods and services it purchases. Its operating expenses will grow too, but its revenues will also rise comparably with inflation.
It's hard to determine the exact impact on public finances because that depends on the source of inflation. Is it mainly oil and energy or imported goods? Right now, it's mainly energy and fossil fuels, and that has a positive effect on public finances.