Well, I'm no expert either, but this is how I see it (economists please correct).
As I understand it, inflated markets collapse as a result of many buyers in the market having invested in assets that have a value that is strongly driven by short term demand. When a perturbing event causes confidence to fail, demand collapses and value collapses. If borrowing has occurred against that value, you get buyers falling further into debt which affects confidence and further expenditure, which makes them fall further into debt, etc. etc.
At the moment, the player market is inflated as a result of careless spending by sugar daddies. A sudden withdrawal of that investment even by one of the major players would cause the player market to shrink rapidly by a certain amount for the reasons just cited, I think.
The player market, however, doesn't really sustain any clubs as businesses. Even clubs that rely on developing and selling players for part of their income are generally spending that income on players, so if the market drops across the board they should survive ok.
Clubs have a relatively inelastic income from rights packages, commercial deals and gates due to the constant demand of fans. This is income that can be counted on to continue to sustain the sport.
However, the proportion of support (the "market share") also has significant inertia, meaning the income from these deals doesn't shift around smoothly in response to price signals. Fans have an untoward degree of brand loyalty in other words.
This means that asymmetric income bases persist and create the conditions for continued bad business decisions. In football, unlike other businesses, the desire for sporting success outweighs the desire for financial success leading clubs to make bad spending decisions. Portsmouth being the shining example of piss poor business management.
But a club might do that under any conditions, I suppose - in an inflated market or a normal one, it has relatively little to do specifically with bubbles, except that the unconstrained spending of sugar daddies exacerbates the income asymmetry and further motivates the bad spending of the poorer clubs. The FFP rules are designed to cope with this problem but they clearly won't eliminated it.
If TV declines significantly as a medium reducing ad revenue, and the net can't be as effectively monetised (doubtful, I think there's fat stacks in the net to be honest) then the income from broadcast packages could go down, but it seems more likely to me that that income will rise as global rights packages are more effectively negotiated. A sharp, prolonged downturn in the value of rights, commercial deals or gates seems unlikely.
The number of leveraged buyouts taking place seems to indicate that most investors in large football clubs are banking on the size of the football sector increasing markedly. The Glazers are a great example of that. They're up to their necks in debt, but every time you hear United's estimated overall value discussed, it's gone up by half a billion quid. Football's preeminence as the strongest sport globally should stand it in good stead as globalisation continues, so it seems like a decent bet to me.
I did see somewhere (think it was Swiss Ramble?) that from an investment perspective, all clubs are seen as loss leading opportunities for capital growth.
