Nothing, in fact if the subvention is ceased that might well be their next step, or they could increase fees and sell debentures like the rest and that isn't going to benefit anyone. Those like Jake who are currently paying through his nose for CIS won't be paying any less.
ESF may be bureaucratic, their staff may be overpaid, their accounts may be in a mess, their admission rules may be flawed, there are perhaps many more holes one can poke, but they are no longer the colonial establishment full of ex-pat children, an outdated image which many ESF critics try to pass off as a basis for their criticism. Old images may die hard, but they should die some day.
Ironically, there was an RTHK programme aired on TV about 4 months ago, in which an ex-pat parent (a British woman) complained that her child was not given an interview by ESF and felt that she was being unfairly "squeezed out by local children" (her exact words). That programme was in Cantonese so I doubt if the likes of Jake would have watched it or understood it if he did.