It's theoretically possible you could convert a world from Windows 10 Edition to regular Java Minecraft, if someone would make a program to convert the data or if MCEdit was able to do that. MCEdit 1.x can open 0.12.1 Pocket Edition worlds (which is what Windows 10 Edition actually is), but as of right now it has trouble exporting the data to schematic files or copying it and pasting into PC worlds. It might be updated and fixed in the future to support that, though. (And in some cases it won't even open the world at all and will just crash.)
As for trying to move a world from PC to Pocket Edition, I'm not sure if that would even be possible in MCEdit, as a lot of blocks in the PC Edition don't exist in Pocket Edition yet (or they are implemented in different ways that make them seem like totally different blocks to the program), so I wouldn't bother with that.
EDIT: Whoops, thought you were talking about converting Windows 10 Edition worlds to PC/Java Edition worlds. There shouldn't be any problem whatsoever (and as the post below says, no conversion at all) when updating to the "full release" of the Windows 10 Edition.