According to publisher Prototype, Clannad will launch both in Japan and worldwide on the Switch early next month, on July 4th. Clannad will be digitally everywhere, but will only launch physically in Japan. Thankfully, all versions support both English and Japanese language options, so if you're craving a physical copy, you can import one. Though the asking price of $44.99 may seem high, it's actually slightly cheaper than the PC version, and the same as the PS4 download version. Clannad will launch worldwide next month, on July 4th.
Also of note is the ESRB "Mature" rating for the Switch version, unlike the existing PS4 version which is only rated "Teen." Clannad has never contained any sexual content, and it seems unlikely that such a beloved VN would come with any changes just for the PS4 version. The ESRB rating is not viewable publicly, nor is the eShop page, so it's unclear at this time what prompted the change. Indeed, the VNDB page for Clannad lists four separate age ratings for the VN, with no indication of any appreciable difference between them.
Still, Clannad is considered a landmark in the visual novel genre, both for developer Key as well as the nakige ("crying game") genre itself. The first of the studio's titles to feature no adult content, Clannad stars high-school delinquent Okazaki Tomoya as he has a chance encounter with a strange girl on his way to school. Tomoya finds himself drawn into one mysterious life after another, as he slowly works to change his high school days for the better. Routinely considered one of the best visual novels ever, it was ported to just about every system in the 2000s, and the latest move to the Switch looks to continue that trend. If you haven't had a chance to check out Clannad yet, you'll get one soon, when it releases on Switch on July 4th.