General Motors filed a trademark application for the term "ZR1" on May 16th with the US Patent and Trademark Office seeking the rights to use it for "motor land vehicles, namely, automobiles." While trademark filings can mean a lot of things, ZR1 would make sense in the Corvette context. The Z06 model came out in 2014, and rumors persist of a coming super-Corvette that could have a mid engine.
GM used the ZR-1 (with the hyphen) on the C3 Vette in 1969 through 1970 and from 1990 to '95 for the LT5-powered Corvette; the ZR1 name was used from 2009 to 2013 with the 638-horsepower supercharged LS9 under the hood. The company still has live trademarks for ZR-1, and there was a ZR1 trademark that the company filed in 1989 and canceled in 2001.