According to the LU "The first staff to wear the uniforms will be on the Central, Waterloo and City and Bakerloo lines on April 25. The uniform change will be completed by July 4......The latest update takes advantage of new and improved fabrics, as well as incorporating modern clothing classics, such as a fleece and polo shirt." I actually thought I'd seen them in advance of that date, as yesterday I saw a woman outside the Waterloo entrance of the Waterloo & Shitty line wearing a reasonable blue fleece. It wasn't quite navy, but certainly looked different from the normal tube blue.
Years ago I remember that Jeff Banks was brought in to design the new uniform for LU staff, but as he was also responsible for designing the Brownies new uniform, I suppose it was no surprise the staff ended up looking a bit like grumpy Thunderbirds puppets.
Not sure who the new designer of the uniforms is, but if their idea of "modern clothing classics" is a fleece and a polo shirt, we should be in for some great trendy apparel. But don't worry we'll only have another five years to put up with the design.