Only a few of the animated films will fall into the Platinum series: Snow White, Beauty & the Beast, Little Mermaid, Lion King...There are 10 all together, but I can't remember all of them, I would guess Lady & the Tramp, 101 Dalmations, Sleeping Beauty would be on the list, but the first four are the only ones I'm sure about.
On the other hand, look at the extras in things like the Sword & the Stone (re-released early this year): an hour-long World of Disney episode and 2 short animateds included in the disk. Disney is slowly getting the clue that we'd like more than just the film before we plunk down our $25 or so.
Disney's not the only one doing this, a lot of studios are releasing a 'Collector's Edition' then a 'Special Edition' then an 'Ultimate Edition' of the same film. My rule of thumb is that I won't buy it unless I'm happy with the extras on it, because chances are that if I wait six months or a year, they'll release it with more stuff. Naturally, I make exceptions to this rule, but unless I absolutely LOVE the movie, I'll try to wait.
Sarangel