According to ChainCatcher, Justin Drake of the Ethereum Foundation answered the question "How many years or months will it take for the Ethereum Foundation's current funds to run out?" in an AMA.
Justin Drake said: "The Ethereum Foundation's financial report will be released soon. EF spends about $100 million per year at current prices, and the EF's main Ethereum wallet holds about $650 million. The Ethereum Foundation (EF) has a fiat reserve that can cover several years of operating funds. (This is the part I know the least about. As Aya mentioned, Ethereum sales were temporarily suspended for regulatory reasons, so the reserves were not replenished until recently.) Roughly estimated, the Foundation has about 10 years of funds in reserve. This reserve can change greatly depending on the fluctuations in the price of Ethereum."
