The extension would make them more likely to trade him, not less IMO. Arenado got dealt with an extension and Story didn't without one. But like I said they are so irrational that you can't really say if he'll be available or not.
And yeah the bat is very average, Steamer thinks it's a wRC+ of 102 this year. But his 3B defense could be elite.
IDK what his contract is exactly for the final 4 years of his deal, overall it was 11.7 AAV. The final four years are probably higher bc it was backloaded but it would his age 29-32 seasons is all.