There's no way they're going to start from scratch and pay for a new restoration, and then mail copies out for free to everyone who bought the first set. That would make them eat a lot more money than they're willing to lose.
The alternative would be to start from scratch but only release it in stores to recover the costs. Fans who hated the first set would have to buy season 2 a second time. Fans would be in an uproar and refuse to pay again. CBS would know that, so there's really no realistic way a redo will work to satisfy both their bottom line and the fans, so this will be "good enough" for the foreseeable future.