Chris Evans was a disaster and will probably be told about it by the ratings of the next episode, but even if they replaced him, which they sadly won't, this incarnation of Top Gear won't work. The main point of TG was its sometimes over-boarding Britishness. It were three blokes trying to delude themselves into believing that Britain was still a great automotive nation and I was usually sitting at home amused by that.
The fact is though, those 22 series of Top Gear are one huge TV ad for Britain. I've learned more about her Majesty's Empire through watching TG than from any other source, at that includes the language, or more precisely, the proper use of it. Nobody could teach the British humour better than May and Clarkson (and no, I don't mean the constant penis jokes)
And now what? One of the main presenters is American. Why? If I want an Americanized TG, I can watch Top Gear USA. And as much as I adore Sabine, she's not exactly British either. They've taken the very core out of TG, and that's why I think it is bound to fail.