If we talk about named storms:
http://www.aoml.noaa.gov/hrd/tcfaq/ns04.jpg
The average is 9.7, and the previous record was in 1995, at 19 (there
were 18 in 1969)
http://www.aoml.noaa.gov/hrd/tcfaq/E10.html
provides a breakdown of averages and least/most years.
Naming was not used consistently before WWII, but the record for
tropical storms in the Atlantic is held by 1933 (21) and therefore this
season will either match or exceed that record, when it is completed.