Please see 2015 Topps 616 (issued in Series 2) as an example of a fairly highly collectible series 2 RC.
Additionally, every year there have been multiple series of cards, there have been RCs in each series.
If that was the case, the Nolan Ryan RC wouldn't be. As well as a host of other very notable RCs.
This information about only a series 1 card can be a RC is INCORRECT.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).