Lots of speculation so will try to go through some of the points.
First off web'n'walk is alive and well and will remain available at it's current £5, though you will be able to select it as a free option an all plans if you don't like the idea of unlimited text.
The new plans are as good as the old plans but with a lot more flexibility. As mentioned you will be able to choose a free booster rather than been forced to have unlimited text. You could have unlimited internet or landline or on net or international boosters (not unlimited). Now the really good bit you can change them each month.
The next great feature is if you choose a lower value handset the line rental reduces accordingly, £10 line rental with unlimited internet anyone? No more ridiculous cash back deals that you stand little chance of getting.
Flext is dead, yep but the market has changed and companies must change to follow the market, this spells the end for flext which is no longer the big seller it used to be. Realistically when you can build your own plan and get a line rental that matches the value of the phone no one will miss it.
Networks must offer 12 month plans under ec rules, blimey could almost hear the nasal tones behind that one :) But in answer that would be sim only 12 month.
Love Flext? Wan't to keep it? No probs, once you have it you can keep it right through the upgrades. T-mobile still has customers on the bronze, silver and gold plans.
Couldn't get a hd2 on upgrade, never heard of that, bear in mind this is the company that will only give N97's to upgrade customers and even bought in I-phones to keep upgrading customers happy. They also gave staff the ability to do better deals to upgrading customers over new, this included a massive training programme and new systems been installed.