Justice Thomas is a great man, and a great American, and I would certainly wish him well if he retires. But he would be sorely missed - having him on the high court is about as close as we can get, to having one of the Founding Fathers/Framers of the Constitution seated there. Read his opinions; he writes like James Madison...
I do agree - Justice Thomas and Justice Alito also are both very Constitutional in their mindset, my hero on the court was Antonin Scalia, greater minds than these would be hard to replace.