I know Google and Intel have a higher growth rate but my guess is Wal-mart Reason...China China's middle class is growing at a rate such that HALF the population will be making more than $10,000 a year by 2010. (only 1 in 5 now) So by 2010, Wal-mart will be offering its "EVERYDAY LOW PRICES" to a target market of about 750 million people!
A company you wouldn't guess would be it now. We could well have a major recession in between and be in a new growth phase in 2020 ... and it could be a new technology so just as Cisco Systems was briefly the highest market cap in the last boom XXXCorp of Malaysia could be the biggy in June 2020. Re Walmart: this wouldn't be the first low cost supplier that couldn't transplant its model to other countries. It might do it but I'll be very surprised if its as good as the MBA courses used to think it was
A company you have never heard of and perhaps does not exist yet. Google was unheard of 10 years ago so in 2020 it will be some new company and with simple inflation and rising prices, it will have an IPO and huge run up and huge market cap. But it will be meaningless as market cap is just a reflection of an inflated price.