If Austin, Lenzy, and Wilkins all move on and Davis comes back, you would be okay with only 7 scholarship receivers to start the season????? And in this scenario, forget about moving someone over to slot (ex Tyree) or Watts back to receiver. Only a foolish team and poor coaching would allow that level of terrible roster management. Injuries/attrition happen, like this year. From March to November, we've had three receivers leave/transfer, two suffer season ending injuries, and one move positions. It's not likely for that to happen again next season, but it wouldn't be impossible either.
Kelly is a believer in having good depth. He wouldn't do that to his new starting QB for 2022.
As much as I want the young guys to get the playing experience, you don't throw away depth (Lenzy) or starters (Austin). Given the track record of receivers here since Kelly was hired, he's very seldom to rely on freshman unless they absolutely have earned it and are prepared.
I'd keep the senior receivers, welcome them all back. Wilkins, I don't know, he's a humble, hard-working young man and maybe his experience in Rees' system could be valuable again, or bring some special teams experience.
Austin, whom some will say has been majorly disappointing, or perhaps overhyped, is still our leading receiver in yards and touchdowns. And this is first real season going against competition that are not his teammates. He may not turn into a superstar, freak like we hoped, but he will be immensely valuable for next years team.