Most other outlets are reporting that the deal is merely close, but if it's already a done deal than Chelsea must be confident something else is going to go through fairly soon. Sturridge, 21, would almost certainly be beind both Kevin Davies and Johan Elmander on Bolton's depth chart but Coyle may wish to include more pace in his attack, and he's faster than both options available to the Trotters right now. The striker, signed from Manchester City in 2009, has made 41 appearances for Chelsea, scoring nine times, although he's also been highly prolific in the reserves.
Although Sturridge is a bit of a favourite amongst fans, this doesn't represent the end of his Chelsea career and is more likely to be helpful in the long run than not. Arsenal prodigy Jack Wilshere benefited immensely from his time at Bolton, and unless this is a loan to buy move (which is unlikely, considering there's no reason for the Blues to sell Danny at this point), this is only a good thing for the future. Chelsea are slightly light on attacking options now, with only Didier Drogba, Florent Malouda, Nicolas Anelka, and Salomon Kalou capable of slotting into their front three.
I'd guess this points to at least one forward coming in before the day's done.