This is actually an interesting topic believe it or not...and it has very little, if anything, to do with Tua himself.
I think we all appreciate that Tua is productive but your feelings on this should tie to how much he's going to cost and whether or not it's good for the Miami Dolphins to sink that into him long-term.
Look at all the QBs who made the Super Bowl from the last 20 or so years who were on rookie deals:
Hurts
Burrow
Mahomes
Goff
Wentz
Wilson
Kaepernick
Eli Manning
Roethlisberger
Grossman
Now look at the QBs who made it on 2nd/3rd deals but who were generally viewed as averaged / replaceable:
Stafford
Newton
Ryan
Flacco
Hasselbeck
McNabb
Gannon
Dilfer
Warner
The point here is that it doesn't take an all-time great or "elite" QB to reach the Super Bowl and moreover, having such a QB doesn't guarantee you'll get more than 1 or maybe 2 shots at it. Peyton dominated with the Colts but only made it twice. Brees dominated with the Saints and only made it once. Philip Rivers famously never got there at all despite some incredible seasons in San Diego.
If you remove some of the repeat offenders that skew the data (guys like Brady, Peyton, Mahomes who were all-time greats who got there repeatedly) you can actually make a case that the best (or at least most common) way to get to the Super Bowl is with a good team which features a rookie-contract QB.
Believe it or not, it's true. Roughly 50% of QBs in the Super Bowl these days are rookie-contract players with many of the other guys being so-so names like Matt Ryan and Joe Flacco who happen to be on the right team with the right players and coaching. The relatively low-cost of the QB plays a huge role and is often their biggest feature. From the random guys like Rex Grossman and Colin Kaepernick to the long-term starters like Roethlisberger, Mahomes and Wilson who simply joined great teams and won the Lombardi in year #2...the list is actually shockingly long and the argument that a 2nd/3rd contract is a huge part of what actually shuts the window is somewhat compelling.
If that's truly the new modus operandi of the NFL then maybe the Dolphins should be planning to replace Tua regardless of how he plays?
The Rams have made the Super Bowl twice in recent memory...each time with a different QB (Goff & Stafford). So have the Eagles (Wentz, Foles & Hurts). If the 49ers get there this year, they'll have done the same (Garoppolo & Purdy). Reaching the Super Bowl has so much to do with the team being good that maybe having turnover at QB isn't as bad as commonly thought. If the team is good, the QB is far more likely to have success anyway, right? Maybe you don't "have to" resign a QB just because he plays well?
I think we all understand the impulse to resign Mahomes, Jackson and maybe Allen to the high-priced contracts they've secured but the problem seems to be securing the "other" guys at reasonable prices. Too often we see a Tannehill at $35M or we're talking about some reasonably solid guy like Prescott, Wilson, Herbert, etc. at $40M. I think that's where teams go wrong. None of those QBs are bad...until you factor in the prices.
It's outside-the-box thinking compared with the conventional "you must secure your franchise QB" thinking which dominates internet forums but nonetheless, it's hard to ignore that Tua's biggest feature this year has that he only cost the Dolphins $10M. No other QB has produced like Tua on a per-dollar basis. The unfortunate reality is that a high-priced extension negates Tua's biggest strength.
It's pretty easy to like your QB when the team's roster is strong and the QB is still on his cheap rookie deal. The real question is whether it's better to retain Tua and buy him a bigger house with a $40M/yr salary or look at the possibility of spending that money on reinforcing the team itself.
Another interesting feature of the "build the team" strategy is that drafting a QB who's a bust (e.g. Trey Lance) doesn't seem to upend the progress the team makes. The 49ers moved right along finding Purdy in the later rounds as did the Eagles with Hurts when his predecessor(s) failed.
Do I think the Dolphins would pass up on Tua? Eh, the pressure to re-sign and to validate Tua's selection seems high so I think Grier would err on the side of re-signing Tua. However, if the team fails to win a Play-off game this year that'll sting. And if Tua struggles with more injury next year it feels like all bets would be off.