They are funded for years, so they won't have to sell any of the foundation's ethereum. They could sell their personal stash but that's not related to foundation's money. I can feel you're starting to regret buying ETC as you can see it slowly being dumped.
They are not funded for years. Last year there was already news that they are running out of funds. This was when they made the Frontier release of Ethereum. Vitalik was calling out for more support from the community. It was almost like he was saying that he is leaving part of the development with the community because they cannot continue it anymore.
Their burn rate is high. I do not know how they spend all that money.