CBS and Viacom (the parent company of Paramount Pictures) have apparently held early talks on a merger, which is a surprising move given the two companies "de-merged" back in 2005. The biggest SFF impact will be on the Star Trek franchise, the crown jewel franchise of both companies which they have - awkwardly - been sharing for the last thirteen years.
When the two companies split back in 2005, Paramount retained the film rights to the franchise whilst CBS walked away with the TV rights. Paramount rebooted the franchise in 2009 with a movie series helmed by J.J. Abrams, consisting of three movies so far with Quentin Tarantino developing a fourth film right now. Meanwhile, CBS instead masterminded an ambitious HD remastering of the entirety of Star Trek: The Original Series and Star Trek: The Next Generation and last year launched Star Trek: Discovery, a brand-new series airing on CBS All Access in the US and on Netflix worldwide.
The split in the franchise has created an awkward lack of cross-pollination between the two sides of the franchise: Star Trek: Discovery had to delay its shooting date due to a legal agreement not to clash with the release of Star Trek Beyond in the summer of 2016. In addition, Discovery was unable to use any material or actors from the Paramount movie series and vice versa.
The re-merger has been proposed in the wake of Disney's monstrous deal to buy 20th Century Fox, which gives them control of a titanic amount of content on top of their previous Marvel and Lucasfilm acquisitions. Disney's power will increase further next year with the launch of a new streaming service, which will be led by a new Marvel show and the first-ever Star Wars live-action TV series. Paramount and CBS want a slice of that kind of action, and see CBS All Access and a merger of their properties as a possible way forward. This may also allow further cross-pollination of Paramount's movie properties to television (although it's difficult to see how, say, a live-action Transformers TV show would work).
What impact a merger would have on either the in-development new movie or Star Trek: Discovery, which is in pre-production on its second season, is unclear.