Same thing happened to me today. I've been playing on the PC primarily. Opened my Realm on my phone to do a quick thing. When I got back to my PC, I spawned at the original world spawn and have no inventory! Very frustrating.
Edit to add : Was able to use a Realm backup to go back to my pre-wiped state.
26 March 2019 my kid's minecraft also switched to Beta without opting in. I'm attaching pictures. On the top of the Minecraft sign in screen, small white letters have appeared that read "beta 1.11.0/7 Gui:4.00" and a second line under that that reads "xbox_one_s, , Xbox One 5 10.0.17763.4088. FP560.0 Server Time: 0.0ms/50ms. Men: 853MB. Highest Mem:1045MB". In the bottom right hand corner of the sign in screen, v.1.11.0.7 appears. All worlds have switched to having the new villager appearance. Villagers will not trade. No progress appears to be lost in the world. Images of an affected world are attached.