Why would we need more nickels? Transactions will end up being rounded to the nearest nickel, which will end up being a dime on one side or a nickel on the other as the smallest necessary coin. Seems like it all evens out.
Both will be used more, the issue with the nickel is that it costs around 14¢ to make one.
I'd have to see a mathematical proof as to why nickels or dimes would be used more, I don't actually think that's the case.
The only logical argument I can imagine is that people are using stacks of 5 pennies now routinely instead of nickels. But personally I never see that happening.