Lauri being traded on a long term contract is the way he gets to a contending team.If Lauri has any integrity, he's not writing an extension after Ainge is done holding these bidding wars. It's a clear indicator that he will be used as a trade piece in the future, no matter what the FO tells him. Considering the timelines, by the time Utah is ready to contend, his descent has likely already begun and would get traded regardless.
So the answer to the original question is yes, he will get traded eventually anyway. And for his sake, I hope he gets traded before he's eligible to extend so he doesn't need to be the one who makes the difficult but correct choice for his career that is not extending. Unless his biggest goal is to advance on the most games play without a single playoff game ladder, which would be a disappointment.
Going to FA only gets him to one of the capspace teams which are usually the scrub teams.
Besides its life changing money and one injury next season could mean he never gets another chance.
Also him signing the deal it has nothing to do with lack of integrity. Its how this business works.