1. A soft opening doesn't have a standard length of time so far as I know, so I imagine Disney does not see this as a problem. Those who are there and have purchased a plan should be able to ask their server or any food-service cast member about their options and get an answer, so the only inconvenience is for those of us trying to plan how we will use credits in the future or those trying to decide whether they want to add a plan to their future trip. Therefore, there's not much need for Disney to rush the announcement, and they'd rather make adjustments during a soft opening than make an official announcement followed by having to announce new changes days later.
2. They will need to do something about using children's credits for adults not on the plan... It's a smaller issue with QSDP in my opinion, but something definitely has to be different from what has been implied with DxDP changes or people can take huge advantage.
Same example I gave in the sticky:
Family of 5 - mom, dad, 3 Disney children (9 or under) traveling with 2 grandparents
Book 2 rooms: first room has mom and kids on deluxe plan, second room has dad and grandparents with no plan
At current prices Deluxe plan is costing them less than $200 for 12 meal credits and 8 snack credits a day
With the proposed flexibility, the four adults can use these credits for three TS meals or a regular TS + Signature TS each day and let the kids eat off their plates or pay child prices for buffets or kids' meals.
In this scenario the adults are paying less than $50 a day (ETA: that's less than Chef Mickey's dinner!) each for a ton of food. They're getting the child price break twice. Either there will be limitations or prices are going to increase significantly for the kids.
3. They'll make it official whenever they're good and ready, but June 22nd (when 2016 packages are released) seems like a decent guess to me. I expect them to increase plan prices and use the announcement of increased plan flexibility to justify/soften the price increase.
MakiraMarlena, I agree that they won't make official exactly what you can substitute, but there still should be an official announcement on the changes. For example, Le Cellier probably won't officially state you can substitute dessert for their cheddar soup, but it should be official that you will have an option to substitute dessert for at least one option out of soup, salad, or fruit. It should be official at QS locations that dessert can be substituted for any snack credit item, but Disney will probably not officially state what qualifies as a snack so that they can change these things on a whim.