Opel and Buick already share a great deal in terms of models and design, with the Buick Regal and Opel Insignia sedans and Encore and Opel Mokka small crossovers being current examples. Buick and Opel's future product lineups could be even more closely-aligned, if a recent trademark filing is an indication.
Opel registered the names Calibra and Cascada with the U.S. Patent and Trademark Office on December 18, 2013. Although Opel is not an actively-marketed brand in the U.S., it is a wholly-owned subsidiary of General Motors. The use of Opel as the registrant was possibly used to disguise GM's intention to use the names on future Buick models. When the short-lived German-built Saturn Astra was sold in the U.S., Opel was also reportedly the registered filer for the "Astra" name.
The Opel Cascada is a two-door convertible based on GM's Delta II platform, which is shared with the Chevrolet Cruze and Buick Verano. The Calibra was a popular two-door coupe sold in the 1990s based on the Opel Vectra, the predecessor of today's Insignia, indicating the possible return of a Regal coupe model in the lineup.
Trademarks are often registered that don't result in models or brands that don't make it to the showroom, but nonetheless indicates consideration of the Opel names for models that could be sold in the U.S.