Unless it's a financial necessity, I don't see much reason for a team that already needs to add a CF to sell one of its existing ones.
Hojlund is still only 22, and in his first season at in the PL his per 90 returns were in line with other B-tier CFs 5-8 years older than him.
PL rates of returns the same or worse than Hojlund's in bold. Also note that most of the better ones are only marginally better. Ages as of the start of this season.
Hojlund (21 years old): 0.17, 0.42.
Watkins (29 years old): 0.48, 0.53, 0.40, 0.30, 0.35
Toney (28 years old): 0.25, 0.43, 0.22
Solanke (27 years old): 0.35, 0.46, 0.19, 0.40
Jesus (27 years old): 0.44, 0.24, 0.44
I don't think it's much of a stretch to think he can develop into a similar B-tier striker given how low the bar is for PL CFs in this current era and how much younger he is than the above players.
If he needs to be sold to bring in a better CF, fine. But otherwise even if you don't rate him much, the upside would seem to be in simply keeping him as the 2nd choice CF we also need to have and hoping he reverts to returning at a similar level to the above. Because it still doesn't seem particularly unlikely he will in the long run.