I have zero hope for Anderson. His control has collapsed, his stuff which was mediocre to begin with is eroding, and hitters have figured out his funky delivery. I hold out some small hope he could be of some use in the pen going full effort but he should never see a major league rotation again.
Allard is a roll of a 20 sided dice. Maybe if you get lucky and it comes up 20 you'll get someone who can fulfill the admittedly low requirements of a number 5 starter. But the odds are pretty low. He fits the long reliever role better.
Elder I have more hope for. He pitched 54 innings in the majors last year and FIP and xFIP show he didn't do half bad. ZiPS loves him. It has him throwing 142 innings with a 3.97 ERA and putting up a 1.5 WAR. That's the same WAR Morton put up last year. I think people are sleeping on Elder a little bit. He's no ace but he could be the one to put your money on winning that 5th spot.
Soroka is anyone's guess. Will he ever get healthy? If he does will he be effective? Who knows?