Assuming most can secure drives for 2010, we have four World Drivers Champions on the grid (Alonso, Raikkonen, Hamilton, Button) plus some race-winning nearly-champions (Massa, Barrichello, Vettel, Webber, Kubica) plus others who either know how to win (Kovalainen, Trulli) or have been threatening to do so for a while (Heidfeld, Rosberg, Glock, arguably Sutil - hmmm, they're all German

). Plus we have constructors who are either on a major high (Brawn, Red Bull) or are threatening to rise again (McLaren, Ferrari), plus a shaken-up grid for next year, with major teams out (Toyota, BMW) and new unknowns in (Campos, Lotus, US F1, Manor, plus the Cosworth engine - will any of them "do a Brawn" this year? Indeed, could we even see the return of Sauber?), drivers in odd places compared to the last year or so, and several new drivers (GP2 heroes Nico Hülkenberg and Bruno Senna [Lalli

] confirmed so far).
Since the retirement of Michael Schumacher, it has been tempting to say that the next season of F1 will be the closest yet - certainly, rather than the straight "Schumi vs. [insert driver here]" fights of the past, 2007 and 2008 were close battles between 3 or 4 drivers, and 2009, while the first half seemed arguably a one-sided anomaly due to drastic rules changes, saw some close battles between about 6 drivers or so, especially in the second half with the resurgence of Ferrari and McLaren. Although, as BAR-Honda proved several years ago, a good season one year doesn't necessarily mean next season is going to be better - it's all in the car development (as McLaren found to their cost this year), yet even teams claiming to be looking to the future like BMW tried to one year (thus putting paid to Kubica's title chances that year) can lag behind in the subsequent season.
Yet, next year, due to the new mix-up and the strengths and confidence of several winning teams and drivers, and the abolition of in-race refuelling and with no teams running KERS (even though it is still technically available in the rules), I genuinely believe things will be much closer still. Button will find it very hard to defend the title easily with all these new changes in the line-up.