I think there's a significant enough distinction between the look of the two shows that—well, that we can call them two separate shows. Davison is closer to Pertwee and Troughton, in some misty semantic way, than he is to Tennant and Eccleston. Hence, I would say that the classic Who you remember from your youth, including Pertwee and before, now also includes Davison and everything up to and including The Curse of Fatal Death. Non-classic Who is from 2005 onward.

Shalka?... grey area.