i would think well beyond 4.

truly dedicate yourself, 5 years......4.5-5 easy. that is really not that high nor that difficult. I would think one could get there just by biking a shit load, not even concerned about a training plan or nothing.

I consider myself very average, bought my first bike (well first bike since a mongoose BMX when I was 12) in December 2008. So, biking just over a year. 3.98 w/kg as of last test, which was a 20 minute test. Last olympic bike leg confirmed results. 305 watts, 76.5 kg.

I have no endurance background at all.

also, I think local pros are well beyond 4.0/kg