Well, Considering that many coins/tokens/projects have many ANNS the number is reduced considerably, Etc, My estimated is 2700-3000 only...........
well i did deduct 236 ..not enough you think ?
New releases have been reduced considerably, Your number It includes takeovers, Duplicated ANNS, However your deduct is a good thing and quick to know the numbers....
However, 70 could be a number a little more accurate so 236-70 equal to 166 its are takeovers,duplicated Anns,etc., Only considering after October 16, 2015.
Edit: So please let me do a comparison beetwen 7236 and 2770-3070 as the number of Total Altcoins until now depending on the approach , criteria and techniques used for this measurement. It would be nice if someone else bring us have his own number for the most accurate.