Once the word is out that we are being forced to sell it becomes a fire sale.
It will surely depend on what the projected shortfall will be come the end of the football season by which point the level of accuracy of that projection should be pretty close to 100% with only a month to a month and a half to go to the end of the accounting period. Some of that will be contingent on any further progress in the FA Cup and finishing position in the league (though neither of which is likely to bring in the big money this season as the FA Cup is not worth much financially and the main financial benefits of potential promotion accrue next season but may be enough to swing it, very unlikely but who knows). Finishing position in itself will also be a factor in our approach as it will obviously have an impact on projections for next season but, as mentioned before, next season at least removes the 2021/22 numbers from the PSR calculation (which will be, what, a loss in excess of £70m? [£92m accounting loss minus around £11m for depreciation & impairments, minus £1.3m loss related to COVID, minus an unknown amount on youth development, women's football & community work]).
Then what would a potential fire sale look like? As you say, hard to offload players you are happy to lose if they are on a good deal here that others won't match. Players coming to end of contracts are obviously not going to be sold, they'll be gone anyway on July 1st. And we cannot sell players we will not make a profit on vs their current book value this season at least. So we are looking at youth products or a select few players we have bought (maybe two of which I'd be desperate to keep) who all would need to be sold in excess of what they are worth on book value. As I say, not that I'd be overly bothered by wholesale changes to this squad generally (but see below) but I am not wholly convinced that it will be necessary financially, one or two may be enough if we can find suitors. The weeks ahead and the announcement of last season's expected loss will give us a better idea.
The biggest danger I think is having a fire sale and exceeding the limit this season as that would almost certainly result in us being unable to register players at some point next season irrespective of whether we can afford to financially or not.
There is nothing we can do financially this year to change any possible transgression of PL rules last but in terms of this year I might be being foolishly optimistic on this (probably) but I am hopeful that we are close enough to the limit that exceeding it is not yet a certainty and that we have enough room to manoeuvre without a mass sale of undervalued players. Like I say foolishly optimistic, I might be very wrong.