from 1541 Ultimate homepage:

Some of you might have noticed that the order form has been temporarily closed, and many questions and rumours have been going around about the future of the 1541 Ultimate. The reason behind all this, is that behind the screens I have been working on a successor of the “1541 Ultimate”. How this unit will be called has not yet been determined, but it could be something as simple as “1541 Ultimate II” or “Ultimate Cartridge”.

What is it, and why was it designed? Basically, it is a scaled down version of the 1541U. It will provide similar functionality, although some things have been changed. It will no longer support full-size SD-cards, but only MircoSD, or “Transflash”. Also, Ethernet will not be supported until further notice. It will support tape emulation out of the box (without the need for special FPGA images) and it will provide a real-time clock function with battery back up. Audio output has been significantly improved, which might seem useless for just the drive sounds, but this enables the creation of FPGA images that provide additional sound channels of useful quality. The power consumption has been reduced as well. There is one extra cool feature that will not yet be disclosed ;-)

And last but not least… This unit will come with a case! At least, that is the plan; there are some negociations going on with manufacturers for plastic insertion moulding. It seems feasible to have this done, although it’s pricy for low quantities. A prototype is 3D-printed this week; the prototype board is already there and functional.

source: 1541ultimate.net