I don't know about Kali, my guess is a big NO.
But for the rest of the 'free' country, the M4 will come in a neutered version.
And 'assault' shotgun is a semi auto with more than one of the following features: PG stock, 5 round mag, detach. mag, folding/collasping stock.
Since the M4 is a semi, it will come with a standard PG fixed stock and 5 round cap., or a non-PG stock and a 'high' cap. tube. Since a M4 coll. stock, is capable of collasping AND has a PG, it counts as TWO evil features and is a big no-no.
I'm still trying to find out if the M4 stock will work on a preban M1. I'm sure the answer is yes, but I doubt Benelli will market the stock by itself, so I'll have to find a dealer to get me one.
The M4 will not be available to civies for a LONG time. My guess is 1-2 years due to military contracts.
If you like the picatinny rail, look into the HK/Fabarms line of shotguns. The FP6 is a pump gun with the rail, and the semi auto version is due out soon. I have one on order...
Or you can add a rail to an M1, but I've yet to do that myself.