As Will and others have explained countless times, music is really something that's personal. The material that you write and rap about comes from experiences and observations. You also have to have the right motivation in order to put out a good album. This is why so many of today's rappers quite literally suck. They realease a new CD every year and they don't give themselves time to experience new things, so their material is recycled. Trucks, Tims, Throwbacks, Air Forces, Clubs, Ice and repeat. Their motivation is to get another album out and get that money, whereas their motivation should be to create an album as good as or even better than their last.
Moreover, you can't expect one of the biggest draws in box office history ever... Yes... EVER... to give up acting, something that he genuinely likes, so that he can go save hip hop, which has made fun of him, shunned him, and then forgotten about him. Saving hip hop is going to take a lot more than Will at 37. The influence that he used to have, and it was frustratingly meager in the past, is even less today. Right now, I'm content with my Lost and Found, Willenium, Big Willie Style, Code Red... you get the picture...