Shawn said 'by' Nov 1st and the tuners 'by' Jan 1st - that means that you could find the tuners on guitars made in December 2019 but after Jan 1st, they expect that NO regular McCarty will be made without the Vintage tuners. There is no guarantee that if you want the TCI 58/15 LT's but with locking tuners, you will find one made between Nov 1st and Jan 1st will be available. They may implement Vintage Tuners on the SC first for example until they can get enough Vintage Tuners in stock to use them on all McCarty models by Jan 1st.
It maybe worth asking whether or not the Phase 3's will fit without the back of the headstock looking like its had its tuners replaced, find out the price of alternative Locking tuners if the Phase 3's don't fit and then add that on to the price you need to get the spec of the guitar you want. I know I want locking tuners so if I do decide to buy a new 594, I will be ordering a set of locking tuners that will fit at the same time.
I am sure it will have some impact on the tone but I am not putting up with regular type tuners and it would be something I would change on ANY new guitar (inc any Custom shop re-issues of vintage instruments) and don't expect non-locking tuners in 2020. I would probably switch to locking tuners on a guitar with a floyd type system with a locking nut because I can't stand wrapping strings around a post when its so easy to just pull the string through and lock it down....