From my understanding the guvmint already has a real good idea what all is out there just by the 4473(s) alone. All of this information is in a database somewhere along with the NIICS information that is NOT supposed to be stored as records. Not all firearms are with the initial purchasers but enough of them are. The guvmint at least knows what has been sold initially.
IMHO what this translates to is the reason for the push for a formal registry (like Canada had but just trashed after 10 years of getting nowhere) is to simply use the existence of it to falsely justify charging another tax. This revenue will allow the Democrats to pocket and spend more of our money they way they want as opposed to WE THE PEOPLE spending the funds the way WE want. The registry will cost nowhere near the amount of tax revenue charged and collected however Congress will lie and claim otherwise to avoid being called out for "taxation without representation". Simply put, this is more communist bullpoopy.
For the longest time I've seen the reason(s) for gun control as basically 50% pushing for it because they are paranoid, dominating and controlling communists that want as little resistance as possible when they move to take over the country. The other 50% calling for gun control doesn't really care about firearms and/or firearms issues at all yet they see 2nd. Amendment issues (like immigration issues) as another political football (for votes) and an extra revenue source.
Both sides are treasonous and need to be dealt with accordingly.