Kyrie Irving can still technically be traded, but all signs point to him playing for Nets next season

Irving's opt-in likely ends the possibility of him joining the Lakers

In purely technical terms, Kyrie Irving opting into the final year and the $37 million or so that came with the remainder of his contract with the Brooklyn Nets probably makes it slightly easier for another team to acquire him. There's no more uncertainty about his status. There's no more fear of him taking a drastic pay-cut next season either. Irving will simply be a player on an expiring contract next season, and players on expiring contracts are pretty easy to trade. 

In fact, they're a good deal easier to trade than impending free agents. When a team acquires a player through a sign-and-trade, they trigger a hard cap at the luxury tax apron—expected to come in at around $155.7 million next season. Irving was reportedly interested in six teams besides the Nets for next season: the Los Angeles Lakers and Clippers, the Dallas Mavericks, the Philadelphia 76ers, the Miami Heat and the New York Knicks. 

The Lakers and Clippers already have so much money on the books that navigating that hard cap would have been nearly impossible. The Heat, 76ers and Mavericks would have struggled as well, though to a lesser extent. Only New York was comfortably in a position to absorb Irving through a trade, and it's not clear that they ever wanted to. So yes, in that sense, Irving opting in removed the hard cap as a possible obstacle. He is easier to trade now than he would have been as a free agent.