Repeat after me:
Canonical needs to "cultivate a sustainable business model" like Chelsea needs to do the same.
That is NEVER. As long as capitalism survives Canonical will survive, because Mark has more money than he can ever spend on Canonical/Ubuntu. He spends more on NY penthouses than he does on Ubuntu. He is not going to have kids (he does not want to and isn't able to anymore).
So Canonical is going to be around forever and will always be able to burn 10s or 100s of millions. No problem. Arguing about how long Mark will keep this up is pretty pointless, when it costs him next to nothing to sustain Canonical. Your common car tuner spends way more of his income on his hobby than Mark.
And just like Chelsea with luck you can win the Champions League with that strategy. There is no reason why Ubuntu can't do the same.