Get both dslr and mirrorless or one high end miorrless?

I would like to start this off by saying this is all hypothetical. I am barely starting my way into photography and want to know everyone's thoughts on this as a future reference. Is it better to keep a mid range dslr (nikon d5300) for stills and sports and get a mid range mirrorless (gh4) for video primarily or to simply get a high end mirrorless (btw i dont know what model would be able to be all around better than both off the top of my head) by selling the d5300. I'm sorry btw if this has been answered before (new here) >_<