The laws regarding NFA weapons don't have any expiration date, unlike the 1994 AWB. Unless Congress acts to repeal the statutes or the Supreme Court finds them unconstitutional the laws regarding NFA weapons will continue. Don't hold your breath waiting for either Congress or the SCOTUS.
The process is fairly simple, though its long and expensive. You need to locate a transferable M16 - one that was made and REGISTERED prior to May 19, 1986. Currently prices for an M16 are in the $10,000 range for a non-Colt gun or conversion, with prices for true factory Colt M16's going for significantly more. Other options include registered sears and "lightning links" (aka auto-disconnectors) which can be installed in an AR15 and will convert it to full auto without the autosear hole a true M16 would have. Drop in sears are about $10k currently and lightning links are about $7k (I have one for sale if you're interested).
If the gun is out of state, you'll need to have it first transfered to a class 3 dealer in your state. If its in your state, it can be transfered directly to you. Whether it comes from an individual or a dealer in your state, you'll need to do form 4 in duplicate (www.titleii.com)
, two FBI fingerprint cards (call BATF), one US citizenship certification, and pay a $200 transfer tax. The form 4 will require you to get a signoff from your local CLEO (Chief law Enforcement Officer - usualy a sheriff, DA, or judge with jurisdiction over the place of your residence).
If you are an FFL, you can have it transfered directly from out of state to your FFL but all other provisions apply (form 4, CLEO signoff, transfer tax, etc.). If its being transfered to a corporation, you do not need to get fingerprints or the CLEO signoff. A word of caution about corporate ownership however - you absolutely need to keep the corporation alive, pay all franchise taxes, fees, file all corporate taxes, etc. If the corporation dies or ceases to exist you will be in possession of an NFA weapon not registered to YOU (since the corporation is the legal owner). IOW the corporation makes transfers faster and easier, but is more of a headache on an annual basis.