It appears that nicotine concentrate will be safe for a while longer, until they know if this will recreate their missing ciggarette revenue.
So, when the regulations go into effect, and more and more people begin DIYing, then they will go after nicotine if their tax revenues are back up to pre e-cig levels.
Just copied this from the FDA regulations:
(Comment 26) Many comments stated that a requirement to prepare PMTAs for all of the many parts and components that go into some of the newly deemed tobacco products would create an effective ban of these products.
(Response) The definition of a tobacco product includes components and parts, and these products are subject to the automatic provisions of the FD&C Act, including premarket authorization requirements. However, at this time, FDA intends to limit enforcement of the premarket authorization provisions to finished tobacco products. In this context, a finished tobacco product refers to a tobacco product, including all components and parts, sealed in final packaging intended for consumer use (e.g., filters or filter tubes sold separately to consumers or as part of kits). For example, an e-liquid sealed in final packaging that is to be sold or distributed to a consumer for use in a finished tobacco product will be subject to enforcement if it is on the market without authorization. In contrast, an e-liquid that is sold or distributed for further 83 manufacturing into a finished ENDS product is not itself a finished tobacco product. At this time, FDA does not intend to enforce the premarket authorization requirements against such eliquids or other components and parts of newly deemed products that are sold or distributed solely for further manufacturing without a marketing order.