There is a new external site which gives really good analysis on how long it will take for players to pop, given age, height and trainer level.
http://bb-training.comuf.com/club/home.php
Contribute to make the stats better. anyways, for your guy, training IS will take 2.3 weeks to pop Inside Shot skill. Training Inside Defence will take 2.1 weeks to pop Inside D
So with those numbers above, unfortunately it does mean that you have been quite unlucky that your guys havent popped yet, but statistically possible.
Train IS for one more week and your guy will pop in both ID and IS i would say. :)