The size of their ground is a complete irrelevance. Premier League clubs get paid so much dosh from TV the number of people coming through the gate is only relevant in terms of creating atmosphere. Bournemouth are the classic example of this, compared to other PL clubs their overheads are...
They are vulnerable on two fronts: if the Russians disappear and take their money back out of the club or if Smug does get tempted elsewhere (unlikely because in his heart of hearts he knows he'll blow it again, but you never know). As long as the money and Smug stay put they'll continue to do...