In addition to LEGO Star Wars 10188 Death Star retiring soon, the UCS DC Comics Super Heroes The Tumbler is also retiring soon as well. It is still currently available at LEGO Shop at Home (USA | Canada | UK). Outside of the official LEGO Shop, Amazon.com (USA) and Walmart.ca (Canada) still has it instock at retail price as well.
The other set that has been added to the retiring soon list includes the hard to find Star Wars 75058 MTT set as well. Thanks to forum member TitanArch for the tip.