He hasn't been sacked.
The BBC has announced that it will not be renewing his contract.
It sounds like semantics, but it's not, there is an important difference.
As a freelance broadcaster, Jeremy Clarkson is under contract for a specific time, and that contract is about to expire.
What the BBC has done is to advise him that they are not renewing that contract, which is slightly better than actually dismissing him under the terms of his current contract.
It probably means that they are able to broadcast the final episodes of Top Gear and more importantly, sell the entire series abroad, which is where the serious revenue comes from.
The futures of his fellow presenters are open to debate, as their contracts also fall for renewal.