“‘Expect to see smart phones accounting for a growing proportion of the wider mobile phone market as they become increasingly affordable to more customers,’ said Canalys Senior Analyst, Pete Cunningham. ‘By 2013, smart phones will grow to represent over 27% of shipments worldwide, with the proportion in some developed markets in Western Europe surpassing 60% and 48% in North America.’”
from here suggests yes.
So if people replace their phones every couple of years by 2015 we could see 50% of people having one in their pocket or bag. That is either a long way off and only half the population or it is really quick and the majority of people. It depends which way you look at it.