I reckon about half who defer won't be back. No criticism, it is how these things work, gradual withdrawal rather than cold turkey.
Come June 2022 it will be 26 months since the last payment, and people will realise they can live without it and are much better off for doing so.
The most interesting games at home are normally in the domestic cups and cost £10 or £15, rather than £35/£40 on a season ticket, and out of a season which could well have 30 home games, going to to 5 key knock out ones for about £60/£70 seems a much better option than paying 10 times as much for 19 generic league games.
With COVID-19 it is like a Tale of Two Cities, some have taken big hits, whilst others are completely unaffected and saved obscene amounts of money with nothing to spend it on and no travel to work costs. So clearly some are gagging at the bit to get back and spend money, whilst others can leave it a year. The last 15 months will definitely, and understandably, changed a lot of people's priorities.