Update: Digital Foundry's Richard Leadbetter shared his own thoughts (via Eurogamer) and believes UE5 will "run on anything" - including Switch, just don't expect it to be on par with the "next-gen" experience revealed:
UE5 gets its first public release early in 2021 with franchise juggernaut Fortnite transitioning across from UE4 later on in the same year. Unlike UE4, however, the new iteration of the engine isn't a clean break from the past. It has the same system targets as UE4, meaning it'll run on anything from the most high-end PCs to old Android and iOS devices, encompassing current-gen consoles too - including Switch. Obviously though, you can't expect the same level of fidelity as the fully-fledged next-gen experience revealed today.
If you game a lot, you've most likely played one powered by Epic's Unreal Engine. Titles like Fortnite run on UE4, while Rocket League uses UE3. Even Nintendo has put the Unreal Engine to use in Switch games like Yoshi's Crafted World.
With this in mind, Epic has just revealed its next-generation engine - Unreal Engine 5. In a detailed post on the Unreal Engine website, Epic explained how it would support current generation consoles and mobile platforms:
Unreal Engine 5 will be available in preview in early 2021, and in full release late in 2021, supporting next-generation consoles, current-generation consoles, PC, Mac, iOS, and Android.
In the same announcement post, Epic said it was designing forward compatibility - so developers could get started on "next-gen" development in UE4 and then transfer their projects across to the new engine when they were ready. Fortnite, for example, will be migrated across to UE5 in mid-2021.
We will release Fortnite, built with UE4, on next-gen consoles at launch and, in keeping with our commitment to prove out industry-leading features through internal production, migrate the game to UE5 in mid-2021.
Introducing “Lumen in the Land of Nanite,” a real-time demo running live on PlayStation 5:
Unreal Engine 5 will be available in preview form early on in 2021, and the full release is planned for later on in the same year. You can read about the capabilities of the new engine over on Epic's blog page.