I'm mostly just wondering what happens if their mining income drops significantly.. like whether or not all current balances would be repaid.
Wait, you're worried a mining company might go belly up and run off with all the invested funds? Pff, that kind of stuff never happens in the bitcoin world...
From what we've seen so far there is every indication that HaoBTC won't do this, they (Eric) have said as much, but you never know. Never invest more than you are willing to lose!