As great as having a home grown talent like Sale as a White Sox is, he should not be viewed as untouchable, and if it makes sense you have to deal him to someone willing to pay premium. Very few players in this game are truly untouchable. Yes, he'd be nice to have to build a staff around, but things look really bleak for the Sox for the foreseeable future, so I say deal him and start stocking up on young (and possibly less injury prone) talent. Basically, you have the White Sox banking that he will stay relatively DL stint-free and live up to his contract, so if another team feels the same way and will give up some top prospects for him, you have to do it and start the rebuild process.
Every team in this division looks like it has plans to, and in some instances is capable of making the playoffs, besides the White Sox and Twins. The Twins started a half-assed rebuild last off-season and it hasn't done them much good. I fear and expect the Sox will do just the same under Hahn.
I would without a doubt rather be bad for a few years than continually mediocre. You get nothing for being mediocre. You get prospects, top talent and a chance to be great and build a consistent contender for being ****ty.