I don't bother. Hell I am making Deffwotch Orks and Grot Guard. Who needs newer models when I can just convert them!
Fun aside, GW has been in a huge "buy them if you want kick" from how much they are diversifying and spreading out these models will likely be in their own kits in a matter of months and I am willing to bet with options outside of the box set. If you want them, cool buy em, if not, meh