McLaren and Williams have almost always been at the same level as ferrari, except this year when oddly both teams got it seriously wrong. But as the 3 biggest teams in F1, with easily the biggest budget I can see them staying at the top for many years to come. Having said that, the big guns, frank williams, patrick head, rond dennis, ross braun etc etc are all getting fairly old. Although I know ferrari know this and are starting to employ serious youth into their team to take over when todt n co retire. Im pretty confident willams and mclaren must be doing the same as the top teams will always get attract the top engineers and so their status as the top teams is likely to reamin for sometime.
Renault and BAR have made good progression this year though and as the constructors standings show they have made a big impact, although last race showed a poor performance from them which could be a sign of them wilting as a result of their small(er) budget which does not enable to develop the car as much as ferrari, williams and mclaren. The more they stay at the toop though, the more money they will get and the more level the playing field becomes.
Next year is going to be very interesting i think. Hopefully williams and mclaren will be back on track, ferrari will undoubtedly be as strong as ever, lets hope renault and BAR keep up this years results and who knows, maybe the people from dubai that are rumored to be buying jordan may come in with a suprise package. This year is ferraris year tho