It would have to be an opener. For someone like Tendulkar at number 4, the chances of India losing two wickets against the likes of Namibia or Holland early enough to give him the chance to make 200 are nil. Also of course if he came in at 2 down for not very many he would have to be sensible to start with because if he played a reckless shot irresponsibly and got out India would be in real trouble.
Hence it has to be an opener - well there are plenty around:
Hayden/Gilchrist
Gibbs
Trescothick
Knight?
Gayle
Astle?
Sehwag
Ganguly?
Probably a couple of others I have overlooked. If you look at the top scores in ODIs, many of them have come against reasonable opposition so that makes it look possible. Gary Kirsten scored 188* off 159 balls against UAE in the 1996 WC in a total of just 321.
Ganguly got 183 off 158 against SL in the last world cup and at the time that was the 4th highest score ever. Dravid also got 145 you may recall (2nd wicket partnership of 318!), as they got a massive 373.
Ironically the two highest scores in 50 over ODIs have been against India, so whenever they are involved there is the potential for lots of runs. I wonder if the tradition for one massive innings in each world cup will continue. Also they tend to come when batting first for obvious reasons so that is a required condition.
Personally I don't think we will see a 200 but a 150+ is very possible. There have been only 27 of these still, yet 15 of them are by current players (ie they seem to be more regular), and 8 of them have been at world cups, so we should see one or two.
For me the grounds in SA tend to be large, although Agemaster said he thinks they are small? Can anyone give information/opinions on this because that will be important. There is only one really high score in SA that is by a guy called David Callaghan who got 169* vs NZ 9 years ago.
Bizarrely he never passed 50 in any of his other 29 ODIs, scoring 324 at 17! He bowled a few overs so looks like a bit of a mediocre all rounder, of course SA were just finding their feet then - the team contained Cronje, Cullinan, Rhodes, De Villiers. NZ had Fleiming, Parore, Rutherford, Crowe, Harris, Doull.