The window for him to emerge off PUP starts after Week 6 of the regular season.
Who knows what sort of shape the Titans will be in at receiver then? At worst for Walter, they are in the same shape, playing well and he's not needed then either. Then he'd get a look for a couple weeks and be put on IR or they'd cut him.
At best for Walter -- not that he'd be rooting for an injury or a failure -- someone will be hurt or have underachieved and they'll be a need for him.