Current volume is ~1.6BTC at day. Say they finally start charging fees, they would make ~$85 a month in fees. Thats a net loss of $415 from just server fee's alone. Your in the hole right off the bat.
I actually got an email from a pretty awesome Bitcoin hosting provider, asking us not to sell and willing to give us free hosting of all our servers to allow us to continue growing without constraints, really a very attractive offer. I think they might be willing to do the same for the buyer so I can always refer the buyer to them.
However if $400 per month is a scary lot for you, this might not be the best project to take over, this is really not just a website but a real startup.