I think the issue here is that Mozilla can't afford to still exist without that 100 million from Google a year. But yeah, I don't see why someone else wouldn't come in and swoop on that.
Last I checked, the statement I read looked like Mozilla had a pile of cash in the bank. Enough to go on for many years if they're not dumb with it.
Would be interesting to see if they've put out an updated statement since then.
The Mozilla Foundation is a non-profit, right? So they should have public documents out there somewhere, right?
Bing?
I don't know much about the search engine partnership issue, but it seems that the author suggested his answer to that. No search service can afford to ignore a browser with over 20% market share.