28y.o. fringe player on last 6 months of contract: sell or extend

I am playing 3rd season for Aston Villa with Trezeguet's contract expiring at the end of this season and I am in mid-season transfer window. He is now 28 y.o., his current salary is 50k/w., certainly a decent to good inside forward/winger for the Premier League but not getting place in the squad anymore.

My dilemma:
At the moment, I have too many wingers/inside forwards who all are younger and on par or stronger than Trezeguet. So he is clearly not needed for the depth. Earlier this season, I sold Bertrand Traore for 40m, so letting Trezeguet on a free is a bit of a waste.

However, if I extend his contract, he asks for +25k/w on his contract and 4 years term. If 3 years, then +50k/w salary.

Will I have issue selling a player at the end of the season if gets a new contract in mid-season? There seems to be only limited interest from a Chinese club to sign him at the end of the season. Which is an option, just get rid of a player who is not needed.

I was burned once when held up for Lansbury for the sake of squad depth and eventually sold him for 400k at the age of 31. Due to age and lack of playing time, he degraded pretty quickly.

I'd sell him, as u said there is possibility you wouldn't be able to sell him a for a decent price in the future. Always look for younger prospects is my rule 1.