It's the retailers decision on when to upgrade. Many choose to upgrade to beta versions in order to be compatible with the latest java version, despite advice from Iress that they don't. The smarter retailers generally choose the option that give their clients the most reliability.
Iress always offer a reliable option or a latest version, they never remove options. If one doesn't suit you then upgrade brokers. A good broker will instantly allow you to open an older proven platform if you have a problem, if yours doesn't then it's not a good broker.
