It may not be possible for Venus to become tidal locked
I don't think we know if it's possible for Venus to become tidally locked. Correia et al. 2008
expect the equilibrium rotation to differ from the synchronous motion
for planets like Venus with thick atmospheres relatively close to the Sun.
This might be best illustrated with a graphic from Auclair-Desrotour et al. 2016:
The gravitational torque is driving towards a tidal lock, but the thermal atmospheric derived torque is in opposition.
Observations may show that Venus is slowing down, according to this esa article. However, according to the article,
the planet could have weather cycles stretching over decades, which
could lead to equally long-term changes in the rotation period
A tidal-locked Venus might not have big day/night temperature variation
This article: The Gale Winds of Venus Suggest How Locked Exoplanets Could Escape a Fate of Extreme Heat and Brutal Cold suggests that the super-fast winds of Venus could occur even if Venus was tidally locked. These winds exceed 100 m/s, which, according to the article is 60 times the surface rotation speed. Even though Venus has an incredibly slow rotation rate currently (~243 days) the difference between night and day temperatures is very small. We wouldn't expect much more deviation if Venus became tidally locked, as the heat transport is primarily driven through various other transport mechanisms than the Sun. A relatively small amount of the Sun's energy makes it to the surface of Venus.
In the comments, uhoh asks about the super-fast winds of Venus:
Is this mechanism keeping Venus' back side warm discussed anywhere in
a peer-reviewed state[...]?
As a quote from Horinouchi et al. (the "SR" in the quote refers to Super-Rotation, which is the super-fast winds):
SR may also occur in tidally locked exoplanets—those that always face
the same way toward their host star and are therefore heated only on
one side. Zonal (east-west) flow around the rotation axis, including
SR, can transport heat from the dayside to the nightside of those
Showman and Polvani go into greater detail in their paper: Equatorial superrotation on tidally locked exoplanets.