Bl00dy reporters have a lot to answer for. That widely quoted £2,500 figure isn't the price cap, which is actually applied to the price per unit. The figure is just an average - some people will use more and have higher bills, others less.
As for April 2023 - it makes sense to review the whole situation then, as the cost of fuel may have sharply decreased by then. A two-year promise of help was always barmy.