Arizona got Hall for a lottery protected 1st and an ok D prospect with good size, plus conditional 2nd/3rd picks. Hall was the best forwards available. No way Isles should give up a 2020 1st if not lottery protected, especially as it is really tough to predict where they may end up this year (too many teams just few points behind them in both East & West conferences and they do have a very tough schedule after the All star break, with both goalies not being that sharp and their best shutdown D not being available). Yes they should not stand by and may need a trade but do not give up a 1st unprotected or top prospect unless the player coming back agrees to a resonable trade & sign deal (similar to what Vegas got for Stone last season). If you miss playoff and the 1st round end up being in the top 3 (which can still happen even if you finish bottom 11 overall) in a strong draft & the UFA does not resign, it will be a huge disaster. Sure prospects are probably 2 years away from helping Isles but if you draft well they can be valuable in future trades to upgrade team and helps to build a strong pipe-line. If you get lucky and land one of the top 3, they can make impact on your line-up maybe even next year.
Example -Canucks owners were reluctant to go for retool but smarten up when they realize their pipeline is just not good enough, even when their window was closing (Sedins last couple of years). Even they could not land top 3 picks each year, they got Patterson (4th overall), Hughes (5th overall), Boeser (23rd overall), and Horvat (10th overall). After compiling the right mix, with a few minor good trades, now Canucks have a team capable of making the playoff and quite entertaining to watch.
I believe Isles with already few good pieces in place, can do the same if they can add a few more blue chips and develop them properly. With a strong upcoming draft, you need to identify the talent/character combination correctly and then provide a strong development environment for them. Stay away from risky type of prospects (like JHS), always go with smart, disciplined, committed team oriented players willing to put in the works for improving and already possess decent to real good skating and puck handling skills. Goal scoring will be bonuses, especially if comes with good wrist shots. Drafting and trades needs to go hand in hand, not over compensating for another. Look at SJ, they went too far all in and now is in a terrible position with an aging team and little prospect in the system for upgrading the team. Worst yet, they do not have the 1st this year and most likely will finish in bottom 10.
Another key area for observation is to see if a player may turn pro is how well they can play without having their heads down on plays in transition and when going into boards and corners. If you do not keep your head up often enough, your NHL career can be cut short as they will be more prone to serious injuries.