This is wishful thinking raised to the Nth degree.
Personally, I don't think it is although on the flip side it's certainly not something that the Ukraine is going to dismiss - the devil will be in the detail, ultimately.
On Russia's side, you've got a far greater amount of resources available to replenish depleted stock compare to Ukraine, who have far more limited resources.
In a war of attrition, they have some advantage. As you rightly mentioned, they
could be of great use against an overstretched army in retreat.
However, the emphasis is on could whereas I'm edging towards the fact that they will not turn the tide - far from it - due to a number of significant factors.
The Ukrainian army isn't in a headlong, disorganised retreat; the Russians are advancing, with some significant gains, but it's slow and very costly.
The RA has faced successful counter-attacks too, so we're in a phase of a much less-fluid conflict: strong defences; lots of FIBUA; to some extent, stagnation.
Tanks are not great for FIBUA (now labelled OBUA due to stigma) or slower offensive duties, and as
@Mutzo Nutzo pointed out at risk from AT weapons.
Then there's the consideration of the standard of these tanks: T80BVs are now primarily reserve tanks. Have they been serviced? Are their parts available?
Known for being notably unreliable if not well-maintained, I'd be surprised if a fair number of these don't break down if they actually reach the front line at all.
You then have to consider how they're going to be deployed and by who because are they replacing depleted tanks and are the troops suitably trained.
Using BA related terminology, is their experience at brigade, regiment, BTn, squadron and troop level to use these tanks as raw recruits will be massacred.
We've already seen a real ineptitude with their armoured formations where there's been little to no screening of armour by the infantry, which is suicidal.
Throwing green troops in would be far from ideal and even more so if those in charge (NCOs to the officers) aren't fully versed in their effective use.
In built up areas and heavily defended locations, slow moving armour with no infantry support will be susceptible to attack from very effective AT weaponry.
Basically, in a long-winded way, this will worry the Ukrainians but not as much as you'd suspect unless there's been a seismic shift in Russian policy*.
*which there won't have been.