will they be releasing one of those "collectors edition gift sets" for the little mermaid like they did for lion king/aladdin/cinderella?

I am thinking yes because it is being released as a Platinum Edition and the 3 titles you mentioned are also Platinum Editions, so if I had to guess I'd say yes...

There were many other Platinum DVD's that came out without a boxset such as Snow White,Lady & the Tramp, Beauty and the Beast, and Bambi

Yeah, but SW and BATB came out before they started doing the giftsets, so they could have just not decided to do them until TLK came out. LATT and Bambi came out in the spring, and they haven't done any sets in the spring. So, their policy could be just to do them only in the fall (probably because of Christmas).

Ahh... a member for 2 years that doesn't know where the search button is. tsk. tsk.

Here is your info in this post which is a part of the general Little Mermaid: Platinum Edition Discussion which was started September a year ago.