Using the data set given, and assuming averaged daily growth between given days, Wikipedia has since 2001-03-07 had an average over all daily growth of 0.632%
The average growth rate (r) between two sampling days was calculated using
1+r=(d2/d1)^(1/n)
where d1 and d2 are the sample amounts on the first and second days and n is the number of days between samplings.
The 0.632% amount is a weighted mean of these results over a period of 551 days. Applying the formula:
n=log(100,000/42021)/log(1+r)
gives 138 days when rounded up to the nearest whole number. Thus the formula projects that article number 100,000 will be reached on 2003-01-24 Using the same techniques, growth in the last 30 days has been at the more modest rate of 0.410% per day. Projecting this gives a figure of 212 days or 2003-04-08