I'd may as well give my two cents on the whole issue as I was not only a fan of TL to start the season (really thought goldenglue would be more than just mid-lane santorin) but also know exactly what their problems are. I'll go down the list from best to worst:
Reignover- Oh how a split changes people. Once regarded as one of the greatest western jg's of all time (even though his roots are from korea), one split on TL has plenty of people (especially on here) trying to shirk 90% of TL's woes on him for some reason. While his effectiveness hasn't been as good as previous splits and his champion pool has been called into question (because hey, apparently you need to be able to play lee sin to be considered "top-tier"), unlike past splits he hasn't really had a lane to gank due to none of his lanes being able to play aggressively without dying. Replace lourlo/goldenglue with huni/fenix or give piglet the right meta, and reignover would probably be in the discussion for mvp right now. Sadly, that is not the case but still doesn't make him to blame.
Piglet- So much hatred for him on here, and I really don't understand why. While yes, he hasn't been "good" this split and has had the meta excuse haunt him for a while, why exactly should TL replace him? On his best days, Piglet is an absolute monster who not only provides veteran leadership but can dominate games as he chooses. Considering the same can only really be said about 2 or 3 NA adc's right now (sneaky, arrow, "possibly" altec?), I'd argue that TL has to keep him as the replacement talent for him is far far worse.
Now that I've talked nice about some of them, it's time to do the exact opposite on the members I personally feel should/need to be replaced ASAP.
Lourlo- Sporting probably the greatest white-guy name of all time (seriously, I'm surprised that he hasn't gone into a game and said "get these m-----ing ganks out of my m----ing lane!" ), lourlo has probably had the biggest stretch of unnoticed mediocrity on an LCS team of all time. Despite posting somewhat weak stats in a 2016 season featuring little toplane competition, TL chose to keep him instead of pursuing the likes of Balls (who wasn't under contract) or Seraph (who despite having slightly worse stats is far more knowledgable). If TL is looking to replace someone in the off-season, Lourlo is probably going to be that guy. As of right now though, they "kinda" have to keep him unless they want to risk going with the likes of RF Legendary (who was replaced by perennial Challenger guy Cris) or bring in a rookie.
Matt- Speaking of unnoticed mediocrity, oh how I really do enjoy it. While I could make another lengthy paragraph about it, I'll just keep it short since, well, tiredness. While Lourlo had the "little top-lane competition" excuse to buff up his stats/go unnoticed, Matt had not just that in spring (let's not forget that it was the period in which people were forced to start players due to visa issues and C9 was doing the hai/fufuu experiment) but also had an ADC carousel to sorta mask up the weaknesses. Considering support is a pretty "bounteous" role and TL have had a potential sub on their roster for a while, we could very easily see him be replaced quite soon with who I thoroughly expected IMT to sign in as their support, a guy by the name of Painless.
Goldenglue- Oh boy do predictions backfire sometimes. Back in the offseason, I was excited to see goldenglue on TL and went on to suggest that because of the stuff I saw on his stream (which was pretty badass, the guy was literally getting a quadra every other game) and with the way the roster was built, he could not just lead TL to around 3rd place but potentially help reignover secure another MVP title. 5 weeks later and it's kinda the same old story that it's always been with him: forced onto mid-lane wave clear mages while being down around 20cs at 15mins and exerting almost no lane pressure allowing guys like keane to look better than they are. While it's almost certain that he will be replaced at some point (it looks like they might try to do the whole "2016 yellowstar" on him), the big question is with who? Link is a weird option as we've heard very little about him recently, Ich could be an interesting option as he showed some quality in a limited sub role for NV, and they "technically" have arcsecond on their roster should they want to allow him to show what he can do on his main role for a change. In either of these cases, I entirely expect TL to spend/go big in the offseason at this position, as they've lacked a top-tier mid in quite some time and would really allow them to exploit reignover's strengths (namely helping out agro lanes).