Only two things could get me to race change at this point: if worgen were given more classes, or if a new race was added that I liked more than tauren.
Assuming all of the updated models were of the same quality (which they should be), how much I like them compared to each other wouldn't change, so tauren would still be my second-favorite race (or maybe favorite if they become better-looking than worgen).
I feel like blizzard will allow everyone either a free race change when the new models release, or possibly take 50% off their fee of a race change. Probably the one that makes them money... But we all know Blizzard isn't that generous.
Most of the races I chose because of how they fit the class I was planning to play (Or well... already had in the case of most of my toons who were faction transfered). I chose Belf for my mage and warlock based on how they looked in caster gear. So, if Belfs magically shrink down to Gnome size, I might switch if something else looked great in caster gear. Overall though, new character models won't influence my race choosing decisions.
New models aren't always attractive. Goblins in cata were a HUGE step up from pre-cata NPC goblins and everyone wanted to be one, but I still think they're god awful to look at. Same with Worgens and Pandas. I'll stick with my basics tyvm.
if draenei males update get a skinnier shoulder span, (thinner? not as wide, idk) I would finally role an alliance pally. Cause right now their shoulder width makes their arms look crazy stumpy. If they had a build closer to broken (in terms of shoulders, not other parts) I would find them to be less goofy. Which I would like, cause I like having a holy elephant mount